The ability of bacteria to cause disease is described in terms of the number of infecting bacteria, the route of entry into the body, the effects of host defense mechanisms, and intrinsic characteristics of the bacteria called virulence factors. Many virulence factors are so-called effector proteins that are injected into the host cells by specialized secretion apparati, such as the type three secretion system. Host-mediated pathogenesis is often important because the host can respond aggressively to infection with the result that host defense mechanisms do damage to host tissues while the infection is being countered
virulence of plant pathogenic bacteria.pptxReddykumarAv
Virulence is a pathogen's or microorganism's ability to cause damage to a host.
In most, especially in animal systems, virulence refers to the degree of damage caused by a microbe to its host.[1] The pathogenicity of an organism—its ability to cause disease—is determined by its virulence factors.[2][3] In the specific context of gene for gene systems, often in plants, virulence refers to a pathogen's ability to infect a resistant host.
BACTERIAL SECRETION SYSTEM by Dr. Chayanika DasChayanika Das
The document discusses various bacterial secretion systems. It describes how the Sec and Tat pathways transport proteins across the cytoplasmic membrane in both Gram-negative and Gram-positive bacteria. It then details six different classes of secretion systems (type I-VI) that transport proteins across the inner and outer membranes. These secretion systems secrete virulence factors and are important for pathogenesis. The document provides examples of pathogenic bacteria that use these secretion systems, as well as key secreted virulence proteins.
Bacterial secretion systems transport proteins across cell membranes. There are seven main types: T1SS through T7SS. T1SS, T2SS, T3SS, T4SS, and T5SS are found in gram-negative bacteria and transport proteins through the inner and outer membranes. T1SS consists of an ABC transporter, MFP, and OMF proteins. T2SS transports folded proteins using an outer membrane complex, inner membrane platform, ATPase, and pseudopilus. T3SS has a base complex, needle, and translocon. T4SS and T6SS can transport substrates between bacteria and host cells. T5SS comes in three classes: autotransport
The document discusses genome evolution in bacterial pathogens. It describes two main ways that phenotypic similarities can evolve between species: parallel evolution where similar mutations arise independently, and collateral evolution where alleles are shared between populations. It provides examples of how pathogenic strains like Shigella arose from E. coli through plasmid acquisition and phenotypic convergence. The document also summarizes key points from a workshop on bacterial pathogen origin and evolution, including the four main forms of genome evolution and the role of horizontal gene transfer in transmitting virulence genes.
This lecture prepared and presented by Ph.D. students : Mohammed Mohsen and Aliaa Hashim
for communication :-
pilotmohammed82@gmail.com
aliaahashim1996@gmail.com
Agrobacterium tumefaciens is a soil bacterium that causes crown gall disease in plants by transferring a segment of DNA (T-DNA) from its tumor-inducing plasmid into the plant genome. The T-DNA encodes genes that result in tumor formation. Virulence genes on the plasmid and bacterial chromosome are required for T-DNA processing, transfer to the plant cell, and integration into the plant nuclear genome, with key roles played by VirD2 and VirE2 proteins. Understanding this natural form of horizontal gene transfer between domains has provided insights into intracellular transport mechanisms.
The cell membrane contains cholesterol and proteins that are vital to many cell processes. Cholesterol levels increase before cell proliferation and help maintain membrane structure. Integrin and NCAM proteins in the membrane allow communication with other cells and the environment to promote cell survival. The membrane also regulates transport of molecules in and out of the cell through passive diffusion, pumps, and carrier proteins. Phagocytosis relies on phospholipases and other molecules to engulf cellular debris. Overall, the complex but foundational cell membrane enables critical functions through its composition and structure.
This lecture introduces concepts of bacterial genetics and virulence. It defines key genetic terms and describes how bacteria differ from eukaryotes in their genetics. Mobile genetic elements often facilitate the acquisition of virulence genes via horizontal gene transfer. Virulence factors do not always benefit the bacterium directly but may aid bacteriophages. Genetic methods like signature-tagged mutagenesis and Tn-seq can identify genes required for virulence in model infections.
virulence of plant pathogenic bacteria.pptxReddykumarAv
Virulence is a pathogen's or microorganism's ability to cause damage to a host.
In most, especially in animal systems, virulence refers to the degree of damage caused by a microbe to its host.[1] The pathogenicity of an organism—its ability to cause disease—is determined by its virulence factors.[2][3] In the specific context of gene for gene systems, often in plants, virulence refers to a pathogen's ability to infect a resistant host.
BACTERIAL SECRETION SYSTEM by Dr. Chayanika DasChayanika Das
The document discusses various bacterial secretion systems. It describes how the Sec and Tat pathways transport proteins across the cytoplasmic membrane in both Gram-negative and Gram-positive bacteria. It then details six different classes of secretion systems (type I-VI) that transport proteins across the inner and outer membranes. These secretion systems secrete virulence factors and are important for pathogenesis. The document provides examples of pathogenic bacteria that use these secretion systems, as well as key secreted virulence proteins.
Bacterial secretion systems transport proteins across cell membranes. There are seven main types: T1SS through T7SS. T1SS, T2SS, T3SS, T4SS, and T5SS are found in gram-negative bacteria and transport proteins through the inner and outer membranes. T1SS consists of an ABC transporter, MFP, and OMF proteins. T2SS transports folded proteins using an outer membrane complex, inner membrane platform, ATPase, and pseudopilus. T3SS has a base complex, needle, and translocon. T4SS and T6SS can transport substrates between bacteria and host cells. T5SS comes in three classes: autotransport
The document discusses genome evolution in bacterial pathogens. It describes two main ways that phenotypic similarities can evolve between species: parallel evolution where similar mutations arise independently, and collateral evolution where alleles are shared between populations. It provides examples of how pathogenic strains like Shigella arose from E. coli through plasmid acquisition and phenotypic convergence. The document also summarizes key points from a workshop on bacterial pathogen origin and evolution, including the four main forms of genome evolution and the role of horizontal gene transfer in transmitting virulence genes.
This lecture prepared and presented by Ph.D. students : Mohammed Mohsen and Aliaa Hashim
for communication :-
pilotmohammed82@gmail.com
aliaahashim1996@gmail.com
Agrobacterium tumefaciens is a soil bacterium that causes crown gall disease in plants by transferring a segment of DNA (T-DNA) from its tumor-inducing plasmid into the plant genome. The T-DNA encodes genes that result in tumor formation. Virulence genes on the plasmid and bacterial chromosome are required for T-DNA processing, transfer to the plant cell, and integration into the plant nuclear genome, with key roles played by VirD2 and VirE2 proteins. Understanding this natural form of horizontal gene transfer between domains has provided insights into intracellular transport mechanisms.
The cell membrane contains cholesterol and proteins that are vital to many cell processes. Cholesterol levels increase before cell proliferation and help maintain membrane structure. Integrin and NCAM proteins in the membrane allow communication with other cells and the environment to promote cell survival. The membrane also regulates transport of molecules in and out of the cell through passive diffusion, pumps, and carrier proteins. Phagocytosis relies on phospholipases and other molecules to engulf cellular debris. Overall, the complex but foundational cell membrane enables critical functions through its composition and structure.
This lecture introduces concepts of bacterial genetics and virulence. It defines key genetic terms and describes how bacteria differ from eukaryotes in their genetics. Mobile genetic elements often facilitate the acquisition of virulence genes via horizontal gene transfer. Virulence factors do not always benefit the bacterium directly but may aid bacteriophages. Genetic methods like signature-tagged mutagenesis and Tn-seq can identify genes required for virulence in model infections.
This document discusses the immune response to helminth infections in three parts. It begins by describing the innate and adaptive immune responses that lead to rejection of helminths, including the roles of cytokines, antibodies, granulocytes, and T cells. It then explains how helminths evade and modulate the immune system to establish chronic infections, such as through regulatory T cells, alternatively activated macrophages, and cytokines like IL-10 and TGF-β that suppress inflammation. Finally, it concludes that while immunomodulation benefits the host by reducing immune-mediated damage, it can also increase susceptibility to other pathogens.
The document discusses the human microbiome and its association with the immune system and various rheumatic diseases. It provides an overview of the types of microbes found in different parts of the human body and their functions. It describes how the microbiome interacts with and regulates the immune system, and how dysbiosis or changes in the microbiome can influence autoimmune responses and the development of diseases like rheumatoid arthritis, spondyloarthritis, inflammatory bowel disease, psoriasis, and systemic lupus erythematosus. Specific microbes and changes in the microbiome composition are linked to several rheumatic conditions based on research using animal models and studies of patient samples. Therapeutic approaches involving probiotics are also
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This document discusses the key concepts of infection and infectious disease. It defines infection as the penetration of a pathogenic microorganism into a host organism, which can lead to an infectious process and potentially an infectious disease. The main factors required for an infection to develop are the presence of a pathogen, a susceptible host, and a site of entry. Pathogenicity and virulence refer to a microbe's ability to cause disease and the intensity of disease caused. Bacteria exhibit several virulence factors including toxins, enzymes, and adhesins that facilitate adhesion, colonization, invasion and damage of host tissues. Infectious diseases progress through distinct phases and can be classified based on factors like duration, localization, and origin of the
The study examines apoptosis in mouse splenic T cell and B cell populations during infection with Plasmodium chabaudi chabaudi AS malaria. High levels of apoptosis were found to correlate with high parasitemia and splenomegaly, particularly in CD4+ T cells. Apoptosis levels decreased as parasitemia was cleared but remained elevated compared to normal mice, with CD8+ T cells and B cells returning to basal apoptosis levels while CD4+ T cells remained higher.
Immuno microbial pathogenesis of periodontal diseaseGanesh Nair
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Bacterial pathogenesis is a complicated process. On encountering a host, pathogenic microorganisms must first adapt to life on the host surface and survive long enough to initiate an infection.
Conferencia de la Dra. Ana María Roa, Bióloga Molecular, sobre Epigenética, impartida en la Universidad Popular Carmen de Michelena de Tres Cantos el 1 de marzo de 2013.
Más información en:
http://www.universidadpopularc3c.es/index.php/actividades/conferencias/event/448-conferencia-una-revision-de-los-conocimientos-fundamentales-de-la-biologia-de-la-celula-la-epigenetica
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This document summarizes a research article that analyzes the structural interaction between YspB, a major translocator protein, and SycB, its cognate chaperone protein, from the Ysa-Ysp type III secretion system of Yersinia enterocolitica. Through bioinformatics tools, the researchers predicted YspB to be highly alpha helical with transmembrane helices, coiled coil regions, and intrinsically disordered regions. They generated a homology model of YspB showing an all-helical, star-shaped structure. Molecular docking revealed the first two tetratricopeptide repeats of SycB interact with helices and loops of YspB that show evolutionary conservation. The
This document provides an overview of the module "Bio305 Pathogen Biology" taught by Professor Mark Pallen. It begins with definitions of key terms like pathogen, virulence, infection, and pathogenesis. It then discusses concepts like the molecular basis of virulence, how bacteria sense their environment and regulate virulence genes, and the steps in successful bacterial infection. It also covers how bacterial sex and acquisition of mobile genetic elements like pathogenicity islands have driven the evolution of virulence. The document provides a sophisticated, multi-factorial view of virulence as a process.
This document provides an introduction to apoptosis, or programmed cell death. It discusses how apoptosis is important for homeostasis and shaping tissues during development. Apoptosis is a highly regulated process where cells self-degrade through molecular machinery like caspases. The document outlines the molecular pathways of apoptosis, including the extrinsic, intrinsic, and execution pathways. It also discusses apoptosis in animals, plants, and the roles of autophagy and caspase enzymes.
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This document summarizes recent research on Chlamydia's type III secretion system (T3SS) and effector proteins. It discusses three key findings:
1) A cryo-electron tomography study revealed that Chlamydia elementary bodies are polarized with T3SS arrays oriented towards the host cell membrane during entry. The arrays redistribute as the bacteria differentiate within cells.
2) A novel effector protein, TepP, was identified that is secreted early in infection and interacts with host cell signaling proteins. Infection with TepP-deficient bacteria altered host gene expression of immune response genes.
3) Chlamydia downregulate MHC-I expression on infected and uninfected cells through
Plants have developed several induced biochemical defenses against pathogens. These include:
1. The hypersensitive response, which involves rapid cell death at the infection site to restrict pathogen growth. This is triggered by specific recognition of pathogen virulence factors.
2. The production of reactive oxygen species and antimicrobial metabolites directly kill pathogens. Defense genes are also induced to produce pathogenesis-related proteins.
3. A hypersensitive response ultimately limits pathogen growth to the initial infection site and induces systemic acquired resistance throughout the plant via signaling molecules like salicylic acid, making the plant more resistant to a wide range of pathogens.
host microbial interaction and toll like receptorsSaiBaba790008
This document provides an overview of host-microbial interactions in periodontitis. It discusses the microbial, immunological, and molecular aspects of this interaction. On the microbial side, it describes how bacteria can adhere to and invade host tissues, as well as evade the host immune response. It also explains how bacteria can directly or indirectly cause tissue damage through virulence factors and enzymes. On the immunological side, it discusses the role of pattern recognition receptors like Toll-like receptors and NOD-like receptors in recognizing microbial patterns and initiating inflammation. It also summarizes the acute bacterial challenge phase where the epithelium responds to bacteria and the early stages of the immune response.
This document discusses Toxoplasma gondii and toxoplasmosis. It covers the parasite's complex life cycle between definitive and intermediate hosts, the molecular mechanisms it uses to invade host cells and evade the immune system, and how host-parasite interactions influence disease pathogenesis. It also examines the genetic diversity of T. gondii populations and emerging research topics, like the potential links between toxoplasmosis and neuropsychiatric disorders. The goal is to provide an in-depth examination of T. gondii and toxoplasmosis for PhD students and researchers.
virulent characteristics of emerging pathogens8146
This document discusses various virulence factors of bacteria. It describes components like capsules, cell walls, adhesins, invasins, toxins, plasmids, bacteriophages, infecting dose, route of infection and communicability. It explains concepts like adaptation, adhesion, invasion, toxigenicity, and dissemination. It provides examples of specific virulence factors for different bacteria like Yersinia enterocolitica, Aeromonas hydrophila and their role in pathogenesis.
Mast cells (MCs) play a broad role in both physiology and disease beyond just allergy. MCs originate from bone marrow progenitor cells and develop in tissues where they exist in different phenotypes. MCs can be activated through various stimuli to degranulate and release mediators that impact wound healing, homeostasis, the nervous system, host defense against parasites, bacteria, viruses, and venoms, as well as diseases like allergy, asthma, vascular disease, and fibrosis. MCs contribute to inflammation in conditions such as inflammatory bowel disease and some autoimmune/autoinflammatory diseases.
1) Bacteria that normally live in the gut can have either symbiotic or pathogenic relationships with their human host. Pathogenic bacteria produce virulence factors that subvert the host's immune defenses, while symbiotic bacteria may secrete regulatory molecules that modulate immunity.
2) The human microbiota interacts with multiple organ systems beyond the gut, influencing metabolism, inflammation, and other physiological processes through molecular signals. Understanding these host-microbiota interactions could lead to new treatments.
3) Studies on the bacterial effector proteins secreted by pathogens like Shigella provide insights into how innate and adaptive immune responses are activated or suppressed. This knowledge may help design new antimicrobials and vaccines.
cell division - Mitosis in plants final.pptReddykumarAv
mitosis is used for almost all of your body’s cell division needs. It adds new cells during development and replaces old and worn-out cells throughout your life. The goal of mitosis is to produce daughter cells that are genetically identical to their mothers, with not a single chromosome more or less.
Meiosis in plant cell system and division.pptReddykumarAv
Meiosis, on the other hand, is used for just one purpose in the human body: the production of gametes—sex cells, or sperm and eggs. Its goal is to make daughter cells with exactly half as many chromosomes as the starting cell.
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The document provides an overview of the inflammatory response in periodontal disease. It discusses how bacterial virulence factors like lipopolysaccharide activate the host immune system through toll-like receptors and pro-inflammatory cytokines like IL-1β and TNF-α are released, leading to tissue damage. It also describes other microbial products like fimbriae, DNA, and enzymes that stimulate inflammation and host mediators that perpetuate the inflammatory response and cause bone resorption and tissue destruction.
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Más información en:
http://www.universidadpopularc3c.es/index.php/actividades/conferencias/event/448-conferencia-una-revision-de-los-conocimientos-fundamentales-de-la-biologia-de-la-celula-la-epigenetica
Transgenic animals are produced by inserting foreign DNA into the animal's genome. There are several methods for producing transgenic animals. The first successful method involved microinjecting a rat growth hormone gene controlled by a promoter into mouse embryos, producing mice that grew larger. Other methods include using embryonic stem cells, viral vectors, cloning, and sperm-mediated gene transfer. Transgenic animals are useful for researching gene function and regulation, modeling human diseases, and potentially increasing agricultural production.
This document summarizes a research article that analyzes the structural interaction between YspB, a major translocator protein, and SycB, its cognate chaperone protein, from the Ysa-Ysp type III secretion system of Yersinia enterocolitica. Through bioinformatics tools, the researchers predicted YspB to be highly alpha helical with transmembrane helices, coiled coil regions, and intrinsically disordered regions. They generated a homology model of YspB showing an all-helical, star-shaped structure. Molecular docking revealed the first two tetratricopeptide repeats of SycB interact with helices and loops of YspB that show evolutionary conservation. The
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Chapter 2
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Chapter 3
Surveying: Object Principles & Types of Surveying; Site Plans, Plans & Maps; Scales & Unit of different Measurements.
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Chapter 4
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Chapter 5
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Chapter 6
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Water Pollution: Water Quality standards, Introduction to Treatment & Disposal of Waste Water. Reuse and Saving of Water, Rain Water Harvesting. Solid Waste Management: Classification of Solid Waste, Collection, Transportation and Disposal of Solid. Recycling of Solid Waste: Energy Recovery, Sanitary Landfill, On-Site Sanitation. Air & Noise Pollution: Primary and Secondary air pollutants, Harmful effects of Air Pollution, Control of Air Pollution. . Noise Pollution Harmful Effects of noise pollution, control of noise pollution, Global warming & Climate Change, Ozone depletion, Greenhouse effect
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1. Palancharmy, Basic Civil Engineering, McGraw Hill publishers.
2. Satheesh Gopi, Basic Civil Engineering, Pearson Publishers.
3. Ketki Rangwala Dalal, Essentials of Civil Engineering, Charotar Publishing House.
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environment for investigating the changes in vegetation cover dynamics. Our study utilizes
advanced technologies such as GIS (Geographic Information Systems) and Remote sensing to
analyze the transformations that have taken place over the course of a decade.
The complex relationship between human activities and the environment has been the focus
of extensive research and worry. As the global community grapples with swift urbanization,
population expansion, and economic progress, the effects on natural ecosystems are becoming
more evident. A crucial element of this impact is the alteration of vegetation cover, which plays a
significant role in maintaining the ecological equilibrium of our planet.Land serves as the foundation for all human activities and provides the necessary materials for
these activities. As the most crucial natural resource, its utilization by humans results in different
'Land uses,' which are determined by both human activities and the physical characteristics of the
land.
The utilization of land is impacted by human needs and environmental factors. In countries
like India, rapid population growth and the emphasis on extensive resource exploitation can lead
to significant land degradation, adversely affecting the region's land cover.
Therefore, human intervention has significantly influenced land use patterns over many
centuries, evolving its structure over time and space. In the present era, these changes have
accelerated due to factors such as agriculture and urbanization. Information regarding land use and
cover is essential for various planning and management tasks related to the Earth's surface,
providing crucial environmental data for scientific, resource management, policy purposes, and
diverse human activities.
Accurate understanding of land use and cover is imperative for the development planning
of any area. Consequently, a wide range of professionals, including earth system scientists, land
and water managers, and urban planners, are interested in obtaining data on land use and cover
changes, conversion trends, and other related patterns. The spatial dimensions of land use and
cover support policymakers and scientists in making well-informed decisions, as alterations in
these patterns indicate shifts in economic and social conditions. Monitoring such changes with the
help of Advanced technologies like Remote Sensing and Geographic Information Systems is
crucial for coordinated efforts across different administrative levels. Advanced technologies like
Remote Sensing and Geographic Information Systems
9
Changes in vegetation cover refer to variations in the distribution, composition, and overall
structure of plant communities across different temporal and spatial scales. These changes can
occur natural.
LAND USE LAND COVER AND NDVI OF MIRZAPUR DISTRICT, UP
MOLECULAR MECHANISMS OF VIRULENCE AND PATHOGENESIS OF PLANT PATHOGENIC BACTERIA.pptx
1. UNIVERSITY OF AGRICULTURAL
SCIENCES, BANGALORE
COLLEGE OF AGRICULTURE V. C. FARM
MANDYA
ASSIGNMENT TOPIC :
MOLECULAR MECHANISMS OF PATHOGENESIS AND VIRULENCE OF
PLANT PATHOGENEIC BACTERIA
REDDY KUMAR A V
PAMM3005
DEPT. OF PLANT PATHOLOGY
2.
3. The terms virulence and pathogenicity, which are often erroneously
considered synonyms. Shurtleff and averre defined that pathogenicity is
the ability of a pathogen to cause disease, whereas virulence is the degree
of pathogenicity of a given pathogen.
Most phytopathogens must evolve strategies to survive in different
environmental conditions to invade and colonize their host known as
virulence factors (Toth et al., 2003).
Bacteria evade, overcome or suppress antimicrobial plant defences using
these virulence factors, which elicit release of water and nutrients from
host cells to colonize in the apoplast successfully.
4. Virulence factors: The molecules that assists the bacteria
to colonize the host at the cellular level.
6. The first step in a successful colonization by pathogenic bacteria is their
ability to maintain close proximity to a mucosal surface by adhesion.
Adhesins are considered as biomolecules such as proteins and
glycoproteins that mediate the binding of the bacteria to the host cell
(Coa et al., 2001).
By irreversible binding with host cell receptors the appropriate
organisms avoid being washed away by the fluids or being thrust out by
ciliated cells.
Bacterial cell adhesion to their host cell depends on the specific binding
to carbohydrates presented at the cell surface which is mediated by
adhesive organelles of bacteria, called fimbria.
Adhesion of bacteria to plant surfaces
7. Plant pathogenic bacteria have evolved numerous sophisticated
strategies for selective transport of proteins and nucleoproteins
involved in the virulence across the cell membrane.
Six major classes of systems implicated in the virulence have been
identified in plant pathogenic bacteria from type I to type VI or
T1SS to T6SS.
In plant pathogenic Gram-negative bacteria, two major systems:
* Single step process in which the secretion proteins are exported
inner and outer membrane without periplasmic step.
* The two steps process namely Sec and the Tat secretion system
are first exported in periplasmic and then transported across the
external membrane to the exterior of bacteria cell.
Secretion system of bacteria
9. Type I secretion system also known as the ATP binding cassette (ABC) transporters.
ABC are involved in the export of various molecules from the cytosol to the
external environment without periplasmic step (Delepelaire et al., 2004).
The type I secretion system have three different proteins that composed of
continuous channel.
ABC proteins transporters is specific outer membrane known as outer membrane
protein (OMP) and also called as membrane fusion protein (MFP) which is
connected to the inner membrane and spans the periplasmic space and extends to
the outer membrane.
Many proteins have great importance in pathogenesis are transferred by ABC
secretion system in plant pathogenic bacteria including proteases, lipases or
performing toxins.
E.g. T1SS required bacteria are Erwinia amylovora and Dickeya chrysanthemi.
Type 1 secretion system
10.
11. T2SS uses a two-step process in which proteins transit the inner membrane
in a Sec- or Tat-dependent process.
The secreted proteins fold in the periplasmic space prior to passage through
an outer membrane secretin pore (Korotkov et al. 2012).
T2SSs are used for the transport of many exoproteins, including proteases,
lipases, and phosphatases.
Examples of T2SS substrates include V. cholerae cholera toxin,
enterotoxigenic E. coli (ETEC) LT toxin, and the P. aeruginosa virulence
factors ExoA (exotoxin A), PlcH (hemolytic phospholipase C), LasA
(staphylolysin), LasB (pseudolysin elastase), PrpL (protease IV), AprA
(aeruginolysin), ChiA (chitinase), and NanH (neuraminidase).
Type 2 secretion system
12. Plant bacterial pathogens have evolved a strategy of delivering an
array of effectors and toxins proteins directly into the cytoplasm
of host cell.
The type III secretion system apparatus is composed of more
than of 20 proteins consisting of basal body spanning both inner
and outer membrane of bacterial cells, and extra needle with the
tip complex extending into the host cell.
T3SS is encoded by hypersensitive response and pathogenicity
(hrp) gene involved in the transfer of Avr proteins in the host cell
(Galan and Collmer. 1999).
Type 3 secretion system
13. • Actin dynamics, mitogen-activated protein kinase (MAPK)
signaling, and nuclear factor-κb (nf-κb)-based inflammasome
activation are modulated by enteropathogenic E. Coli (EPEC),
enterohemorrhagic E. Coli (EHEC), P. Aeruginosa, and V.
Cholerae T3SS effectors.
• Y. Pestis yop effectors also affect these signaling pathways as well
as facilitating intracellular persistence within macrophage.
• The intracellular pathogens C. Trachomatis, S. Enterica, and S.
Flexneri require T3SS effectors to invade and persist within the
vacuolar system of host cells.
14.
15. The type IV secretion system is present in both the Gram-
negative and positive plant pathogenic bacteria (Wallden et al.,
2010).
This translocation system that deploy the sec gene to transport
the pathogenicity factors from the inner bacterial cell or into the
extracellular environment or directly into the host cell.
T4SS, which are structurally related to DNA conjugation
systems, have the ability to transport DNA, DNA-protein
complexes, and protein effectors across membranes.
Type 4 secretion system
16. Agrobacterium tumefaciens that target the oncogenic
dna-protein complex in the plant cell.
N. Gonorrhoeae uses a T4SS to acquire virulence genes
through horizontal gene transfer mechanisms.
L. Pneumophila inject ~330 effector proteins that affect
multiple host processes, including vesicle trafficking,
autophagy, host protein synthesis, host inflammatory
response, macrophage apoptosis, and host cell egress.
H. Pylori uses the T4SS to insert effectors that modulate
the host immune response.
Examples for T4SS
17. Type 5
secretion
system
This type V secretion system is present in Gram-negative bacteria (Tseng et al.,
2009). It is one of the simplest secretion pathway.
The T5SS translocation system is dedicated to transfer a single specific
polypeptide known as the passenger domain in two step process:
1. Sec translocator across the inner membrane.
2. The transportation of the passenger through the outer membrane by forming a
outer memebrane pore.
The virulence factors associated with T5SS passengers includes biofilm
formation, adhesions, toxins, enzymes productions and cytotoxic activity
(Huang and Allen. 1997).
18. Examples of T5SS effectors include:
Adhesins (B. Pertussis FHA, pertactin and Bapc, E. Coli
AIDA-I and ag43, H. Influenzae hia, HWM1, and HWM2,
Shigella flexneri Icsa, Y. Enterocolitica yada)
Proteases (N. Gonorrhoeae and N. Meningitidis iga
Protease, S. Flexneri sepa)
Toxins (H. Pylori vaca).
19. Type 6
secretion
system
The contact-dependent T6SS uses a phage-tail-spike-like
injectisome structure to deliver effectors not only to host
cells but also to competitor bacterial species, thereby
giving pathogens competitive advantages within certain
host growth niches.
This system also includes in formation of biofilm, the
quorum sensing and antibacterial toxins (Benali et al.,
2014).
20. T6SS effector
Functions Bacteria
Adherence E. coli, C. jejuni, V.
parahaemolyticus
Host cell invasion E. coli, C. jejuni, S.
enterica, P.
aeruginosa, Y.
pseudotuberculosis
Actin dynamics E. coli, V. cholerae
Host immune
responses
K. pneumoniae,
V .Parahaemolyticus
21. Production of plant cell
wall degrading enzymes
Plant cell walls consist of three major polysaccharides such as cellulose,
hemicellulose and pectin, in woody and some other plants, lignin.
The number of genes coding cell wall degrading enzymes varies include
pectinases, proteases, cellulases and xylanases. Proteases are secreted by the
T1SS, whereas the rest of the above said enzymes by the T2SS (Preston et al.,
2005).
Pectinases to be most important in pathogenesis, because they are responsible for
tissue maceration by degenerating the pectic substances in the middle lamella and
eventually, for cell death.
Four major types of pectin degrading enzymes are secreted viz. pectate lyase,
pectin lyase, pectin methyl esterase and polygalacturonase.
Among these pectinase enzymes, pectate lyases (Pels) are largely involved in the
virulence of soft rot Pectobacterium species.
22. Cell wall degrading enzymes are believed to play a role in
pathogenesis by facilitating penetration and tissue
colonization, but they are also virulence determinants
responsible for development of symptom once growth of the
bacteria has been started.
A few Xanthomonads, e.g., X. campestris pv. campestris, the
causal agent of black rot of crucifers, have genes for two
pectin esterases and polygalacturonases, four pectate lyases,
five xylanases and nine cellulases.
Other deprived pectinolytic bacteria include A. tumefaciens,
which has only four genes encoding pectinases of any form
and Xylella, which has only one gene coding for a
polygalacturonase.
23. Productions of bacterial
toxins
Toxins play a vital role in pathogenesis and parasitism of plants by several plant
pathogenic bacteria.
Plant pathogenic bacteria are known to produce a wide range of both specific and
nonspecific host phytotoxins. Some are polypeptides, glycoproteins others are
secondary metabolites.
These toxins acts by using diverse mechanisms from modulating and suppressing
plant defence response to alternation and inhibition of normal host cellular metabolic
process.
P. syringae pv. syringae, the cause of many diseases and kinds of symptoms in
herbaceous and woody plants, generates necrosis-inducing phytotoxins,
lipodepsipeptides, which are generally categorized into two groups, such as mycins
and peptins (Melotto et al., 2006).
Chlorosis inducing phytotoxins include coronatine formed by P. syringae pv.
atropurpurea, glycinea.
24. Coronatine biosynthesis plays an important role in virulence of toxin-
producing P. syringae strains.
Coronatine is also believed to induce hypertrophy of storage tissue, thickening
of plant cell walls, accumulation of protease inhibitors, compression of
thylakoids, inhibition of root elongation and stimulation of ethylene
production (Alarcon-Chaidez et al., 1999).
25. Extracellular polysaccharides (EPS) may be connected to the bacterial cell
as a capsule, be produced as fluidal slime, or be present in both forms.
EPS play a significant role in pathogenesis of many bacteria by both direct
interference with host cells and by providing resistance to oxidative stress.
EPS1 is the chief virulence factor of the bacterial wilt disease caused by R.
solanacearum in solanaceous crops (Milling, et al., 2011).
EPS1 is a polymer made of a trimeric repeat unit consisting of N-acetyl
galactosamine, deoxyl-galacturonic acid and trideoxy-d-glucose, where it is
produced by the bacterium in huge quantity and constitutes more than 90%
of the total polysaccharides.
Xanthan, the major exopolysaccharide secreted by Xanthomonas spp., plays
a key role in X. campestris pv. campestris pathogenesis.
Production of extracellular
polysaccharides
26. Production of phytohormones
Biosynthesis of the phytohormones, auxins (e.g. indole-3-
acetic acid-IAA) and cytokinins are major virulence factors
for the gall-forming plant pathogenic bacteria, Pantoea
agglomerans pv. Gypsophilae.
Ethylene, the gaseous phytohormone formed by several
microbes including plant pathogenic bacteria, can also be
considered a virulence factor for some of them
P. savastanoi pv. Phaseolicola (Weingart et al., 2001).
27. QUORUM SENSING AND BIOFILM PRODUCTION:
It is a bacterial communication mechanism that regulates the density of
microbial population using the gene expression in response to the
environment (Kanda et al., 2011).
This molecules are also known as autoinducers. Quorum-sensing signal
N-acyl homoserine lactones are known to regulate numerous virulence
factors including enzymes production and exopolysaccharides in many
plant pathogenic bacteria.
E. g. in E. amylovora a series of regulators namely MqsR, QseBC and
exporter TqsA.
Biofilm is a complex multilayer cellular structure attached to a tissues and
embedded with an exopolysaccharide. Several plant pathogenic bacteria
have been considered as biofilm producer as virulence factors including
X. compestris and P. syringae (Keith et al., 2003)
30. Disease symptoms caused by some bacterial pathogens of plants and
representative virulence mechanisms used by these pathogens
31. Plant pathogenic bacteria employ a sophisticated array of molecular
mechanisms to cause disease in plants. Key virulence factors include
toxins, cell wall-degrading enzymes, and secretion systems.
Secretion systems (T3SS) are crucial virulence determinants, injecting
effector proteins directly into plant cells to modulate host physiology.
Quorum sensing enables coordinated gene expression, facilitating
virulence factor production and biofilm formation. Furthermore, some
bacteria produce phytotoxins like phaseolotoxin, disrupting cellular
processes and causing disease symptoms.
Understanding these molecular mechanisms is crucial for developing
strategies to combat plant pathogens. Targeting virulence factors,
disrupting communication systems, and enhancing plant immunity are
promising approaches. Future research aims to unravel complex
interaction networks and develop sustainable solutions for plant disease
management.
CONCLUSION
These protein secretion pathways are also used to deliver bacterial proteins and toxins into the host environment or directly into host cells across one (inner cell membrane), two (Gram-negative outer membrane), and/or three (host membrane) hydrophobic phospholipid bilayers.
Gram-negative pathogens can transport proteins into and across the inner cell membrane
using either the SecYEG translocase machinery, which is part of the general secretion (SecDEFGY) pathway for unfolded proteins and it is powered by ATP or the twin arginine translocation (Tat) pathway for folded proteins for example iron sulfur bacteria and cytochromes which is powered by Proton motive force.
Examples of T1SS substrates include exotoxins (Bordetella pertussis (Whooping cough) pertussis toxin PTx, adenylate cyclase toxin CyaA), RTX toxins [uropathogenic E. coli (UPEC) HlyA hemolysin, V. cholerae RtxA], adhesins (S. enterica SiiE), proteases (P. aeruginosa AprA), and heme-binding proteins (P. aeruginosa HasA).
RTX Toxins- it is toxin super family is a group of cytolysins and cytotoxins produced by bacteria.
T2SSs are structurally related to the machinery used to assemble type IV fimbriae.
LT toxin – heat liable toxin
These virulence determinants have the capacity to modulate the physiological functions of the host.
T3SS use one-step processes to directly inject bacterial proteins (effectors) into host cells.
The assembly and function of these secretion systems involve a conserved set of proteins that create macromolecular structures spanning the bacterial inner and outer membranes and the host cell membrane.
Each system secretes its own set of effectors, which vary between pathogens. Regardless, the primary function of all of these effectors is to manipulate host cell processes, including signal transduction pathways, actin cytoskeletal rearrange-ments, intracellular vesicle transport and stability, and host immune responses.
T3SS “injectisomes,” which are structurally related to the flagellar apparatus, are used by many Gram-negative pathogens to deliver effectors into a wide variety of host cells.
Plant cell walls consist of three major polysaccharides such as cellulose, hemicellulose and pectin, in woody and some other plants, lignin.
Plant pathogenic bacteria employ a sophisticated array of molecular mechanisms to cause disease in plants. Key virulence factors include toxins, cell wall-degrading enzymes, and secretion systems. Toxins like coronatine and syringolin manipulate plant hormonal pathways, disrupting defenses and promoting disease progression. Cell wall-degrading enzymes such as cellulases and pectinases facilitate bacterial entry and nutrient acquisition.
Type III secretion systems (T3SS) are crucial virulence determinants, injecting effector proteins directly into plant cells to modulate host physiology. These effectors manipulate immune responses, alter hormone signaling, and promote bacterial survival. Additionally, type IV secretion systems (T4SS) contribute to virulence by delivering effectors and promoting bacterial colonization.
Quorum sensing enables coordinated gene expression, facilitating virulence factor production and biofilm formation. Furthermore, some bacteria produce phytotoxins like phaseolotoxin, disrupting cellular processes and causing disease symptoms.
Understanding these molecular mechanisms is crucial for developing strategies to combat plant pathogens. Targeting virulence factors, disrupting communication systems, and enhancing plant immunity are promising approaches. Future research aims to unravel complex interaction networks and develop sustainable solutions for plant disease management.