3 morphology & cell biology of bacteria

Morphology & Cell Biology of Bacteria,[object Object],Siti Sarah Jumali (ext 2123),[object Object],Room 3/14,[object Object],sarah_jumali84@hotmail.com,[object Object]

The basic morphology of a cell,[object Object]

1. The Cell Membrane,[object Object],Phospholipidbilayer: 2 surface layers of hydrophilic of polar head and inner layer of hydrophobic nonpolar tail.,[object Object],Peripheral proteins: Function as enzyme scaffold for support and mediator for cell movement,[object Object],Integral proteins: disrupting lipid bilayer. Other types known as transmembrane protein,[object Object],Glycoprotein: protein attached to the carbohydrate,[object Object],Glycolipid: Lipid attached to carbohydrate,[object Object]

Membrane structure,[object Object],Fluid mosaic model,[object Object]

Characteristics of Lipid bilayer,[object Object],Semi-permeable,[object Object],Consists of : 1) hydrophilic,[object Object], 2) hydrophobic ,[object Object],Main function is to:,[object Object],Protect cell (as outercovering),[object Object],Keep the things that are on the inside of a cell inside, and keep what things are outside the cell on the outside. ,[object Object],It allows some things, under certain situations, to cross the phospholipidbilayer to enter or exit the cell.,[object Object]

Function of the Cell Membrane,[object Object],Protective outer covering for the cell. ,[object Object],Cell membrane anchors the cytoskeleton (a cellular 'skeleton' made of protein and contained in the cytoplasm) and gives shape to the cell.,[object Object],Responsible for attaching the cell to the extracellular matrix (non living material that is found outside the cells), so that the cells group together to form tissues.,[object Object],Transportation of materials needed for the functioning of the cell organelles without using cellular energy.,[object Object],The protein molecules in the cell membrane receive signals from other cells or the outside environment and convert the signals to messages, that are passed to the organelles inside the cell.,[object Object],In some cells, the protein molecules in the cell membrane group together to form enzymes, which carry out metabolic reactions near the inner surface of the cell membrane. ,[object Object],The proteins help very small molecules to get transported thru cell membrane, provided, the molecules are traveling from a region with lots of molecules to a region with less number of molecules.,[object Object]

The cell membrane,[object Object],Lipid bilayer of plasma membrane,[object Object],Lies between two dark line,[object Object],Prokaryote have less sterol as compared to the eukaryote, causing rigid structure,[object Object],Less-sterol wall in prokaryote is Mycoplasma,[object Object],Taken with TEM,[object Object]

2. The bacterial cell wall,[object Object],Has peptidoglycan,[object Object],Marks the difference between gram +ve and gram –ve bacteria,[object Object]

Peptidoglycan,[object Object],Polymer of disaccharide,[object Object],Also known as murein,,[object Object],is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of bacteria (but not Archaea), forming the cell wall.,[object Object],The sugar component consists of alternating residues of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM). ,[object Object],Attached to the N-acetylmuramic acid is a peptide chain of three to five amino acids.,[object Object]

3 morphology & cell biology of bacteria

3. Cell wall of Gram negative and positive,[object Object]

Gram positive and Gram negative,[object Object]

Gram positive and Gram negative bacterial cell walls,[object Object],A, Gram positive bacterium thick peptidoglycan layer contains teichoic and lipoteichoicacids. ,[object Object],B, Gram negative bacterium thin peptidoglycan layer and an outer membrane that contains lipopolysaccharide, phospholipids, and proteins. The periplasmic space between the cytoplasmic and outer membranes contains transport, degradative, and cell wall synthetic proteins. The outer membrane is joined to the cytoplasmic membrane at adhesion points and is attached to the peptidoglycan by lipoprotein links.,[object Object]

Peptidoglycan in Gram positive bacteria,[object Object],Linked by polypeptides,[object Object]

Gram positive bacterial cell wall,[object Object],Teichoic acid,[object Object], - Lipoteichoic acid links to plasma membrane,[object Object], - Wall teichoic acid links to peptidoglycan,[object Object],May regulate movement of cations,[object Object],Polysaccharides provide antigenic variation,[object Object]

Gram negative bacterial cell walls,[object Object]

Gram negative bacteria outer membrane,[object Object],Lipopolysacharides, lipoproteins, phospholipids,[object Object],Forms the periplasm between the outer membrane and the plasma membrane,[object Object],Protection from phagocytes, complement and antibiotics,[object Object],O-polysaccharide antigen e.g. E. coli O157:H7,[object Object],Lipid A is an endotoxin,[object Object],Porins (proteins) form channel through membrane,[object Object]

The Gram stain Mechanism,[object Object],Crystal violet-iodine crystals form in cell,[object Object],Gram positive,[object Object], - Alcohol dehydrates peptidoglycan,[object Object], - CV-I crystals do not leave,[object Object],Gram negative,[object Object], - Wall is lesser or,[object Object], - Wall is made up of pseudomurein (lack NAM and D-amino acids),[object Object]

Acid-fast organisms are difficult to characterize using standard microbiological techniques (e.g. Gram stain - if you gram stained an AFB the result would be an abnormal gram positive organism, which would indicate further testing), though they can be stained using concentrated dyes, particularly when the staining process is combined with heat. Once stained, these organisms resist the dilute acid and/or ethanol-based de-colorization procedures common in many staining protocols—hence the name acid-fast.,[object Object]

Atypical Cell Wall,[object Object],Acid-fast cell wall,[object Object], - e.g gram positive,[object Object], - Waxy lipid (mycolic acid) bound to peptidoglycan,[object Object], - Mycobacterium,[object Object], - Nocardia,[object Object]

Atypical Cell Wall,[object Object],Mycoplasmas,[object Object], - Lack cell walls,[object Object], - Sterols in plasma membrane,[object Object],Archaea,[object Object], -Wall-less or Wallas of pseudomurein (lack Nam and D-amino acids),[object Object]

Cell Wall-less Forms ,[object Object],Few bacteria are able to live or exist without a cell wall.,[object Object],The mycoplasmas are a group of bacteria that lack cell wall.,[object Object],Mycoplasmas have sterol-like molecules incorporated into their membranes and they are usually inhabitants of osmotically-protected environments. ,[object Object],Mycoplasmapneumoniae is the cause of primary atypical bacterial pneumonia, known in the vernacular as "walking pneumonia". For obvious reasons, penicillin is ineffective in treatment of this type of pneumonia. Sometimes, under the pressure of antibiotic therapy, pathogenic streptococci can revert to cell wall-less forms (called spheroplasts) and persist or survive in osmotically-protected tissues. When the antibiotic is withdrawn from therapy the organisms may regrow their cell walls and reinfect unprotected tissues. ,[object Object]

Damage to the cell wall,[object Object],(Gram –ve): Lysozyme digests disaccharide in peptidoglycan,[object Object],(Gram +ve): Penicillin inhibits peptide bridges in peptidoglycan,[object Object],Protoplast is a wall-less cell,[object Object],Spheroplast is a wall-less gram positive cell,[object Object], - Protoplasts and spheroplasts are susceptible to osmotic lysis,[object Object],L forms are wall-less cells that swell into irregular shapes,[object Object]

External structures,[object Object],Many bacteria have structures that extend beyond or surround cell wall,[object Object],Flagella and pili extend from the cell membrane through the cell wall and beyond,[object Object],Capsules and slime layers surround the cell wall,[object Object]

4. Bacterial Cell Surface Structures,[object Object],Arrangements of Bacterial Flagella,[object Object],Monotrichous: Bacteria with a single flagellum located at one end (pole),[object Object],Amphitrichous: Bacteria with 2 flagella one at each end,[object Object],Peritrichous: Bacteria with flagella all over the surface,[object Object],Atrichous: Bacteria without flagella,[object Object],Cocci shaped bacteria rarely have flagella,[object Object]

Polar Monotrichous flagellum,[object Object],Vibriocholerae,[object Object]

Amphitrichous flagella arrangement,[object Object],Spirillum,[object Object]

Lophotrichous flagella arrangement,[object Object],Spirillum,[object Object]

Structure of flagella in gram –ve and +ve bacteria,[object Object]

Chemotaxis,[object Object],Bacteria move away or towards subtances that are present in the environment through a nonrandom process,[object Object],Positive chemotaxis: movement towards attractants (nutrients),[object Object],Negative chemotaxis: movement away from the repellent ,[object Object]

Pili,[object Object],Pilus (singular),[object Object],Tiny hollow projections,[object Object],Used to attach bacteria to surfaces,[object Object],Not involved in movement,[object Object],Long conjugation,[object Object],Short attachment pili (fimbriae),[object Object]

E. coli (14,300X),[object Object]

Glycocalyx,[object Object],Capsule & Slime Layer ,[object Object],Used to refer to all polysaccharide/polypeptide containing substances found external to cell wall,[object Object],Capsule,[object Object],Slime layers,[object Object],All bacteria at least have thin small layer,[object Object]

5. Glycocalyx,[object Object],Capsule ,[object Object],More firmly attached to the cell wall. ,[object Object],Have a gummy, sticky consistency and provide protection & adhesion to solid surfaces and to nutrients in the environment.,[object Object],Bacteria that possess capsules are considered encapsulated, and generally have greater pathogenicity because capsules protect bacteria, even from phagocytic white blood cells of the immune system. ,[object Object],The adhesive power of capsules is also a major factor in the initiation of some bacterial diseases.,[object Object],Slime Layer,[object Object],A glycocalyx is considered a slime layer when the glycoprotein molecules are loosely associated with the cell wall. Bacteria that are covered with this loose shield are protected from dehydration and loss of nutrients.,[object Object]

Capsule,[object Object],Protective structure outside the cell wall of the organism that secretes it,[object Object],Only certain bacteria are capable of forming capsules,[object Object],Chemical composition of each capsule is unique to the strain of bacteria that secrete it,[object Object],Encapsulated bacteria are able to evade host defense mechanism (phagocytosis),[object Object]

Slime Layer,[object Object],Less tightly bound to the cell wall and is usually thinner than the capsule,[object Object],Protects the cell against drying, traps nutrients and binds cells together (biofilms),[object Object]

Biofilms,[object Object],A microbial community that usually forms slimy layer or hydrogel on a surface,[object Object],Bacteria attracted by chemicals via quorum sensing,[object Object],Composed of populations or communities of microorganisms adhering to environmental surfaces.,[object Object],The microorganisms are usually encased in extracellular polysaccharide that they synthesize.,[object Object],Can be found in sufficient moisture is present. ,[object Object],Their development is most rapid in flowing systems where adequate nutrients are available,[object Object]

Biofilms,[object Object],Biofilm usually begins to form when free swimming bacterium attaches to a surface,[object Object],Share nutrients,[object Object],Shelter from harmful factors,[object Object]

Thoughts for the day..,[object Object],What is the biofilm that forms on teeth called?,[object Object]

Case Study,[object Object],Delayed Bloodstream Infection Following Catheterization ,[object Object],Patients with indwelling catheters received contaminated heparin with Pseudomonas fluorescens,[object Object],Bacterial numbers in contaminated heparin were too low to cause infection,[object Object],84–421 days after exposure, patients developed infections,[object Object]

Functions Of The Bacterial Envelope,[object Object]

3 morphology & cell biology of bacteria

3 morphology & cell biology of bacteria

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3 morphology & cell biology of bacteria