2. Introduction
Bacterial growth
1. Bacterial growth curve
2. Kinetics of microbial growth
3. Bacterial growth in vivo
4. Factors affecting microbial growth
Bacterial metabolism
1. Components of metabolism
2. Role of ATP
3. Metabolic Pathways of energy generation
Bacterial flora in oral cavity
A. actinomycetocomitans and P. gingivalis
Conclusion
References
3. Life on Earth is famous for its diversity.
Throughout the world we can find many millions of different forms of
life.
Biologic classification helps identify each form according to common
properties using a set of rules and an estimate as to how closely
related it is to a common ancestor in a way to create an order.
4.
5. Eukaryote, any cell or organism that possesses a clearly defined
nucleus.
Has a nuclear membrane that surrounds the nucleus, in which the
well-defined chromosomes are located.
also contain organelles, including mitochondria, Golgi apparatus,
endoplasmic reticulum and lysosomes.
- “Encyclopædia Britannica”
6. Prokaryote is any organism that lacks a distinct nucleus and other
organelles due to the absence of internal membranes.
The cell membrane is made up of phospholipids and constitutes the
cell’s primary osmotic barrier.
The cytoplasm contains ribosomes, which carry out protein
synthesis, and a double-stranded deoxyribonucleic acid (DNA)
chromosome, which is usually circular.
- “Encyclopædia Britannica”
7.
8. Based on energy source
Phototrophs
• Use light as an energy source; photosynthesize.
Chemotrophs
• Use inorganic and organic chemicals.
Based on carbon source
Autotrophs
• Use carbon dioxide.
Heterotrophs
• Do not use carbon dioxide as their carbon source
9.
10. Cells are the most fundamental units of life.
All living organisms are made of one or more.
Cells reproduce by copying their genetic material and then
dividing—a parent cell giving rise to daughter cells.
Types of Cell Division:
1) Binary Fission
2) Mitosis & Meiosis
It refers to an increase in cell numbers, not in cell size.
11. The reproduction of prokaryotic
cells (bacteria and bacteria-like
Archaea) is accomplished through
binary fission.
A bacterial cell that is ready to
divide first copies its genetic
material, called the nucleoid—a
single, circular chromosome of
DNA (deoxyribonucleic acid).
The two chromosomes, each
attached to the plasma
membrane, move apart as the cell
elongates.
12. Once the two copies of genetic instructions are separated, the cell
divides, laying down new cell wall and membrane between the two
chromosomes.
Binary fission is essentially cloning.
Barring mutations that may have occurred when the genetic material
was copied (a process called replication), the two resulting daughter
cells are identical to the parent cell.
16. Illustrates the dynamics of growth
Phases of growth
1. Lag phase
2. Exponential or
logarithmic (log) phase
3.
4. Stationary phase
5. Death phase (decline phase)
17. During this phase, bacteria are growing in size, but they are not
undergoing binary fission.
Hence, there is no increase in cell number.
The bacteria are adapting to the new environment and are
synthesizing cellular components such as ribosomes, enzymes, and
other proteins.
Bacteria have the maximum cell size towards the end of the lag
phase.
18. This phase is also referred to as the exponential phase because
there is a logarithmic increase in cell number.
This exponential growth is expressed as the bacteria’s generation
time.
During this phase, the conditions are optimal for growth and binary
fission occurs.
In the log phase, cells are smaller and stain uniformly.
19. There is no net increase or decrease in cell number in this stage. In
other words, cell growth (division) equals cell death.
The birth rate decreases due to limited nutrients, lack of space, and
the build up of secondary metabolic products (e.g. toxins).
The insufficient supply of nutrients also causes some bacteria to
form spores during this phase.
Cells frequently are gram variable and show irregular staining due
to the presence of intracellular storage granules.
20. This phase is characterized by an exponential death of cells.
When the media runs out of nutrients and there are too many
toxins, cells begin to die at a faster rate.
Involution forms are common in the phase of decline.
21. 1. Water
2. Oxygen
3. Carbon dioxide
4. Temperature
5. Hydrogen ion concentration
6. Light
7. Osmotic pressure
8. Symbiosis and antagonism
22. Moisture is essential for the life of bacteria. Most processes taking
place in a bacterial cell are in a water base.
80% of bacterial cell consists of water.
Dehydration is detrimental for most bacteria eg. Treponema
pallidum. But some like staphylococcus can resist drying for months.
Spores are particularly resistant to dessication and may survive in
the dry state for several decades.
23. Most life forms depend on oxygen for survival & growth.
Microrganisms require oxygen to act as terminal electron acceptor
in their respiratory chain.
AEROBE = bacteria which require oxygen for growth.
ANAEROBES = bacteria which do not require oxygen for growth.
OBLIGATE AEROBE = bacteria which grow only in the presence of
oxygen. Eg. Pseudomonas, bacillus.
FACULTATIVE ANAEROBE = bacteria which are aerobes but can
grow with lack of oxygen or in absence of oxygen. Eg. Streptococci
24. MICROAEROPHILIC = bacteria which grow with trace amount of
oxygen. Eg. Listeria monocytogenes
OBLIGATE ANAEROBES = bacteria which strictly grow in the
absence of oxygen. They may die on exposure to oxygen. Eg
clostridia, bacteroides.
AEROTOLERANT ANAEROBES = anaerobes which do not
require oxygen but tolerate the presence of oxygen.
25. Approximately half of dry weight
CO2 is provided by cellular metabolism and from environment.
Autotrophic organisms are able to use carbon dioxide as source of
carbon.
Heterotrophic bacteria require some amount of carbon dioxide from
exogenous sources.
5-10 % CO2 is supplied for them in culture.
Capnophilic = requiring excess amount of CO2 eg Brucella abortus
(10% CO2).
26. The carbon available in the carbohydrate sugar molecules is cycled
further by microorganisms in a series of reactions that tricarboxylic
acid (or TCA) cycle.
The breakdown of the carbohydrate serves to supply energy to the
microorganism.
This process is also known as respiration.
In anaerobic environments, microorganisms can cycle the carbon
compounds to yield energy in a process known as fermentation
27. PSYCHROPHILES = bacteria which grow below 20°C, e.g. soil and
water saprophytes. Up to -7°C reported.
MESOPHILES = bacteria which grow between 20-40°C. e.g.. Most
pathogenic bacteria are mesophiles. Wide range e.g. Pseudomonas
5-43°C, narrow range e.g. Gonococcus 30-39°C.
THERMOPHILES = bacteria which grow at higher temperature i.e.
60-80°C. e.g. Bacillus stearothermophilus. Up to 250°C reported.
28. THERMAL DEATH POINT = The lowest temperature that kills a
bacterium under standard conditions in a given time.
Under moist conditions most vegetative, mesophilic bacteria have a
thermal death point 50 to 65°C and most spores between 100 and
120°C
29. The pH requirement of bacteria is also variable.
Most bacteria have an average pH requirement of 7.2-7.6 which
matches with pH in human body environment.
Some bacteria grow in acidic pH. Eg lactobacilli in pH=3.
Some bacteria grow in alkaline pH. Eg. Alkaligenes at pH = 10.5
30. Most bacteria prefer darkness for growth.
Cultures die if exposed to sunlight.
However some bacteria require sunlight and are called phototropic.
Exposure to light may influence pigment production.
Photochromogenic mycobacteria form a pigment only on exposure
to light and not when incubated in the dark
31. There is a wide range of osmotic tolerance found in bacteria.
0.5% NaCl is added in culture media to provide suitable osmolarity.
PLASMOLYSIS = Sudden exposure to hypertonic solutions may
cause osmotic withdrawal of water and shrinkage of protoplasm.
This occurs more readily in gram negative than in gram positive
bacteria.
PLASMOPTYSIS = Sudden transfer from a concentrated solution to
distilled water may cause plasmoptysis (excessive osmotic
imbibition leading to swelling and rupture of the cell).
32. Nitrogen: Found in all the amino acids, nitrogenous bases of
nucleic acids, etc.
Hydrogen: found in all biological molecules, Carbs, fats, proteins,
nucleic acids, etc
Phosphorous: found in nucleic acids, ATP, and phospholipdids of
membranes
Sulfur: found in 2 or 3 amino acids of microbes
Trace elements: inorganic elements needed in very tiny
concentrations (manganese, cobalt, Zn, Cr)
s
33. Generation time : The time required for a bacterium to give rise to two
daughter cells under optimum conditions is known as generation time.
Kinetics of microbial growth : unicellular organisms divide by binary
fission each cell grows to full size, replicates its genetic material then
divides into identical daughter cells , leading to exponential increase in
cell numbers.
1 2 4 8 2 n
34. This is done by repeatedly transferring bacterial cells into fresh
medium of identical composition.
Transfer is done while they are multiplying in exponential phase.
Two techniques are used:
Chemostat device
Turbidostat device
Maintenance of bacteria in continuous culture is sometimes
necessary in industrial and research purposes.
35. In vitro and in vivo growth patterns of bacteria are different as the
environmental conditions are different.
In vivo growth of bacteria depends on our nutritional status,
immunity, hormonal factors, pH, redox potential etc.
There is a significant difference in the growth patterns of bacteria in
human body and artificial medium.
36. Despite an apparent simplicity, bacteria can form complex
associations with other organisms. This process is known as
symbiosis.
Symbiosis - defined as the living together in more or less intimate
association or close union of two dissimilar organisms
The organisms that live together in such relationship are called
Symbionts.
4 types :
MUTALISM
COMMENSALISM
PARASITISM
SYNERISIM
37. A type of symbiotic interaction in which both organisms benefit from
the relationship in some way.
In humans, gut bacteria assist in breaking down additional
carbohydrates, out-competing harmful bacteria, and producing
hormones to direct fat storage.
38. The harmless strains are part of the normal flora of the gut, and can
benefit their hosts by producing vitamin K2, and preventing
colonization of the intestine with pathogenic bacteria
39. one organism benefits while the other organism neither benefits nor
suffers from the interaction.
Humans are host to a variety of commensal bacteria in their bodies
that do not harm them but rely on them for survival.
e.g. staph epidermis on skin
40. Parasitic relationships, in which one species benefits and the other
suffers, are very common in nature.
Most of the microorganisms studied in medical microbiology are
parasitic and feed on human tissue.
For e.g., cholera, leshmaniasis, and Giardia are all parasitic
microbes.
41. METABOLISM = the series of changes of a substance
(carbohydrate, protein, fat) that take place within the bacterial cell
from absorption to elimination is known as metabolism.
CATABOLISM = breakdown of macromolecules into simpler
micromolecules, absorption into cell, conversion into basic blocks
including interconversion of ADP to ATP.
ANABOLISM = a process by which the basic building blocks are
utilized in synthesis of various cellular structures such as monomers
and polymers.
42. Aerobic bacteria obtain their energy and intermediates only through
OXIDATION and energy is provided by ATP (oxidative
phosphorylation).
Anaerobic bacteria obtain their energy by FERMENTATION
(substrate level phosphorylation).
Facultative anaerobes may act in both ways.
43.
44. Glucose is a key energy-storing molecule
Nearly all cells metabolize glucose for energy
Glucose metabolism is fairly simple
Other organic molecules are converted to glucose for energy
harvesting
45. Enzymes
Adenosine triphosphate (ATP)
Energy source
Electron carriers
Precursor metabolites
biological catalyst, facilitates
each step of metabolic reaction
by lowering the activation of
energy reaction.
Serves as energy currency of
cell
Compound that is oxidized to
release energy, also called as
electron donor.
Carry the electrons that are
removed during oxidation of
energy source.
Intermediate metabolite that link
anabolic & catabolic pathway.
Components Functions
46. The overall equation for the complete breakdown of glucose is:
C6H12O6 + 6O2 6CO2 + 6H2O + ATP
The main stages of glucose metabolism are:
o Glycolysis
o Cellular respiration
47. Glycolysis
Occurs in the cytosol
Does not require oxygen
Breaks glucose into pyruvate
Yields two molecules of ATP per molecule of glucose
48. If oxygen is absent fermentation occurs
Pyruvate is converted into either lactate, or into ethanol and
CO2
If oxygen is present cellular respiration occurs
49.
50.
51. Many bacteria have another pathway in addition to glycolysis for
degradation of glucose.
1. Pentose Phosphate Pathway
2. Entner Doudoroff Pathway
52. Hexose monophosphate shunt
Occurs simultaneously with glycolysis & provide breakdown of both
pentose sugar and glucose.
Intermediate pentoses are used for nucleic acid synthesis,
aminoacid synthesis
Important producer of reduced coenzyme i.e. NADPH used for
biosynthetic reaction.
Stuart Hogg Essential microbiology 2nd edition John Wiley & Sons.Ltd 2005
53.
54. Uses 6-phosphogluconate dehydratase and 2-keto-3-
deoxyphosphogluconate aldolase to create pyruvate from glucose.
Most of gram –ve bacteria like pseudomonas, rhizobium,
agrobacterium.
Produces 1 molecule NADH, 1 molecule NADPH and 1 molecule of
ATP
Stuart Hogg Essential microbiology 2nd edition John Wiley & Sons.Ltd 2005
55.
56. Cellular respiration - pyruvate obtained from glucose breakdown are
channeled either to respiration or fermentation.
Requires oxygen
Breaks down pyruvate into carbon dioxide and water
57.
58.
59. Last phase of respiration which generate ATP from reduced
substrates.
Consists of a sequence of carrier molecules through which electron
passes.
Occurs in plasma membrane.
Electron transport chain is different in different bacteria.
60.
61. Fermentation is the process of extracting energy from the oxidation
of organic compounds, such as carbohydrates, using an
endogenous electron acceptor, which is usually an organic
compound.
In contrast, respiration is where electrons are donated to an
exogenous electron acceptor, such as oxygen, via an electron
transport chain.
62.
63.
64. The colonization of the oral cavity starts close to the time of birth.
Within hours after birth, the sterile oral cavity will be colonized by low
numbers of mainly facultative and aerobic bacteria.
It is estimated that more than 700 different species are capable of
colonizing the adult mouth and that any individual typically harbours
150 or more different species. (Moore WE, 1994)
Most oral bacteria are harmless commensals under normal
circumstances.
65. The process begins with the colonization of habitat by pioneer
microbial populations.
In oral cavity of newborns, streptococci are the pioneer organisms.
They fill the niche of the new environment and modify the habitat
and new population develops.
66. 1. Buccal epithelium (soft tissue)
2. Dorsum of the tongue
3. Supragingival tooth surface
4. Subgingival tooth and crevicular epithelial surfaces
67.
68.
69. Biofilm is an association of micro-organisms in which microbial
cells adhere to each other on a living or non-living surfaces within a
self-produced matrix of extracellular polymeric substance.
Biofilm formation is a multi-step process starting with attachment to
a surface then formation of micro-colony that leads to the formation
of three dimensional structure and finally ending with maturation
followed by detachment.
The dental plaque biofilm also has similar structure.
70. The term ‘Biofilm’ was coined by Bill Costerton in 1978.
The term Biofilm (Wilderer and Charaklis 1989) describes the relatively
indefinable microbial community associated with a tooth surface or any
other hard non-shedding material, randomly distributed in a shaped
matrix or glycocalyx.
Biofilm is “a microbially derived sessile community characterized by
cells that are irreversibly attached to a substratum or interface or to
each other, embedded in a matrix of extracellular polymeric substances
that they have produced, and exhibit an altered phenotype with respect
to growth rate and gene transcription.” Donlan and Costerton 2002
71.
72. Dental plaque has been defined as “a specific but highly variable
structural entity consisting of micro-organisms and their products
embedded in a highly organized intercellular matrix.”
It represents a true biofilm consisting of a variety of micro-organisms
involved in a wide range of physical, metabolic and molecular
interactions.
Lang NP, Mombelli A, Attstrom R. Oral Biofilms and Calculus. In: Lindhe J, Lang NP,
KarringT, editors. Clinical Periodontology and Implant Dentistry. 5th ed. Oxford:
Blackswell- Munksgaard; 2008. pp. 183–267.
73. Dental plaque (WHO 1978)
Is defined as specific but highly variable structural entity resulting
from sequential colonization & growth of microorganisms on the
surfaces of teeth & restoration consisting of microrganisms of
various strains and species embedded in the extracellular matrix,
composed of bacterial metabolic products & substances from
serum, saliva & blood.
75. The term Actinobacillus actinomycetemcomitans was coined by
Topley and Wilson.
Member - Actinobacillus Family – Pasturellaceae
Given the name Actinobacillus actinomycetemcomitans, that is,
derived from the Greek words, actes- meaning ray , because of
the star on the top of the agar colony and, Mycetes meaning
fungus, because Actinomyces was originally thought to be a
fungus.
The Latin word Comitans, meaning in common with, or
accompanying Actinomycetes spp.
76. Studies found similarity of A. actinomycetemcomitans and
Haemophilus aphrophilus, H. paraphrophilus, and H. segnis,
suggesting the new genus Aggregatibacter for them.
The species of the genus Aggregatibacter are independent of X
factor and variably dependent on V factor for growth in
vitro.(Nørskov-Lauritsen N; Kilian M, 2006)
Related A.a to Juvenile periodontitis (Newman, Socransky and
Slots 1976)
77. Fastidious
Facultatively anaerobic
Non-motile
Non-sporing
Non-hemolytic
Small gram-negative rod, 0.4–0.5 lm x 1.0–1.5 lm in size
Oxidase +ve and Catalase +ve
78. Blood agar or chocolate blood agar supplemented with 5–7%
defibrinated horse blood if incubated in an aerobic atmosphere
supplemented with 5– 10% carbon dioxide.
are generally round with an irregular edge, domed and colourless
in appearance, and may have central wrinkling and adhere to the
agar surface.
The pale colour of the agar allows light to be transmitted through the
agar, and lighting the agar plate from underneath allows easy
discrimination of the internal structures.
Adherent, catalase-positive colonies, with star-like internal
structures, that reduce nitrates to nitrites are characteristic of A.
actinomycetemcomitans
80. belongs to the phylum Bacteroidetes
is a nonmotile, Gram-negative, rod-shaped, anaerobic,
pathogenic bacterium.
It forms black colonies on blood agar.
has been considered as one of the putative periodontal pathogen.
Colonizes periodontal pocket and spreads into deeper tissues,
including connective tissue and bone.
P.gingivalis is frequently isolated from subgingival plaque samples in
patients with adult and other forms of periodontitis.
81. Major oral ecologic niche for this species appears to be subgingival
plaque
Possess significant proteolytic activity.
P.g is at present the only known porphyromonas species isolated
from human that produces phenyl acetic acid as a metabolic end
product.
82. Asaccharolytic and black pigmented rod that form greenish-black
colonies in blood agar plates (Haffajee and Socransky, 1994).
Fresh clinical isolates of this organism have different colony
morphologies, ranging from smooth to rough colony morphotypes
(Reynolds et al., 1989).
84. The original isolate, identified as a “fusiform Bacteroides,” was
first reported in the literature by Tanner et al. in 1979.
Is an non motile,
spindle-shaped,
highly pleomorphic rod and
gram negative obligate anerobe
85. It grows slowly only on anerobic conditions
Needs several growth factors such as N-acetylmuramic acid
Produces several proteolytic enzymes that are able to destroy
immunoglobulins and factors of complement system.
89. C. rectus is a Gram negative, anaerobic, short, motile vibrio.
The organism is unusual in that it utilizes H2 or formate as its
energy source.
Grows anaerobically with dark pigmentation when sulfide is added
to the medium, which is transformed to FeS, giving a gray stain
90. Getting well acquainted with the bacterial growth & metabolism
helps to
Discrimate between the various growth patterns of
microorganisms.
Association of microorganisms with specific disease.
Determine the treatment plan necessary for the disease.
91. Stuart Hogg Essential microbiology 2nd edition John Wiley &
Sons.Ltd 2005
Alternatives to binary fission in bacteria. E. R. Angert. Nature
Reviews Microbiology (2005) vol. 3, pp. 214-224
Newman MG,Takkei HH, Klokkevold PR, Caranza FAJr. Caranza’s
Clinical Periodontology 10th edition St Louis. Missisouri Saunders
Elseveir Inc 2006:s
Audesirk, Audesirk & Byers, Biology: Life on Earth 10th edition
Pearson Higher Ltd 2013
Pudlo NA, Urs k, Kumar SS, German JB, Mills DA, Martens EC
Symbiotic Human Gut Bacteria with Variable Metabolic Priorities for
Host Mucosal Glycans MBio. 2015 Nov 10;6(6):e01282-15
Is the second phase of aerobic respiration.
Pyruvate formed enters TCA cycle only after converted into acetyl CoA by decarboxylation.
From TCA cycle oxidation of one Acetyl CoA molecule produces 3 NADH,1 FADH & 2GTP
NADH and FADH2 donate their energetic electrons to the carriers of the transport chain. As the electrons pass through the transport chain, some of their energy is used to pump hydrogen ions from the matrix into the intermembrane space.
This creates a hydrogen ion gradient that is used to drive ATP synthesis.
At the end of the electron transport chain, the energy-depleted electrons combine with oxygen and hydrogen ions in the matrix to form water.
Also known as fermentation 2 types alcohol fermentation and lactic acid fermentation.
Formation of a biofilm is a complex process that follows several distinct phases, beginning with adsorption on to the tooth surface of a conditioning film derived from bacterial and host molecules, which forms immediately following tooth eruption or tooth cleaning. This adsorption is followed by passive transport of bacteria mediated by weak long-range forces of attraction. Covalent and hydrogen bonds create strong, short-range forces that result in irreversible attachment.
