bacteria Structure Flashcards
What are glycocalyces?
Gelatinous, sticky substances surrounding the outside of the cell.
What does glycocalyces contain?
Polysaccharides , polypeptides, or both
Where are two types of glycocalyces. What are they?
Capsule and slime layer
Describe the structure of a capsule of the bacteria?
Composed of organized repeating units of organic chemicals. And is firmly attached to the surface of the cell.
What is the purpose of the capsule?
Protects cells from drying out and may prevent bacteria from being recognized and destroyed by host
What is a slime layer of a bacteria?
A sticky layer that allows prokaryotes to attach to surface. It is loosely attached to the cell surface. It is water souble and protects cells from drying out.
Examples of bacteria that has a slime layer
Pseudomas, streptococcus mutans uses is a gensus that adheres To the teeth of humans and can cause tooth decay because it uses sucrose to synthesis a biofilm teeth.
What is a flagellum?
The flagellum is a long protein structure responsible motility .
How does a flagellum work?
By spinning like a propel, using proton motive force as energy, the flagella pushes like a ship .
Bacteria with a flagellum can cause disease . Name one?
Helicobacter pylori is a bacterium that causes disease. It has a powerful flagellum at one end of it spiral shaped cell, it allows H.pylori to penetrate the vicious mucous gel that coats the stomach.
The flagellum is composed of three parts. What are they?
Filament, hook, basal body
Describe the filament structure of the flagellum?
Is made up of a protein called flagellin. The flagellin is arranged in a helical structure with a hollow core.
Describe the hook portion of the flagellum.
Connects the filament to the cell surface and is curved.
Describe the basal body of the flagellum
Basal body anchors the flagellum to the cell wall and the cytoplasmic membrane
What does monotrichous mean?
Having a single flagellum at only one pole or end. E.g. Vibrio sp
What does peritrichous mean?
Having cilia or appendicular organs around a bacterium e.g ecoli
What does lophotrichous means?
Having two or more flagella at one end. E.g. Pseudomonas sp
What does amphitrichous mean?
Having a flagellum at both ends e.g spirilum
What is the purpose of bacterial flagella structure?
Movement
What protein makes up bacterial flagella structure?
Flagellin, deposited in a helix at the lengthening tip
Facts about the bacterial flagella structure?
Base of filament inserts into hook
Filaments capsule of rotating 360 degree
What anchors filament ?
Basal body anchors filament and hook to cell wall by a rod and a series of either two or four rings of integral proteins.
Sex pilus
Used for the transfer of DNA , longest pilus , it is used to join the two cells for e.g ecoli.
What are pilus ?
Hair like projections of the cell
What are endospores?
Dormant cell,
Produced when starved,
Resistant to adverse conditions such as temp,organic solvent.
What is the chemical that is in endospores?
Calcium dipicolinate
Example of bacteria with endospores
Bacillus and clostridium
What is the structure of endospores?
Peptidoglycan layer, cortex, between two membranes, less cross linked, dehydrated muramic acid (lactam)
Definition of cell wall
Consist of cell membrane, cell wall included embedded proteins and glycocalyces or capsule.
Functions of the cell wall
Barrier ( osmotic protection, regulated environment (ph, solute gradients) Solute transport Electron transport Electrochemical gradients/ ATP synthesis Motility Lipid biosynthesis Protein secretion
What is attached to the phosphates on the cytoplasmic membrane structure
Calcium ions and magnesium ions
Function of Permeability barrier
Prevents leakage and functions as a gateway for transport of nutrients into and out of the cell.
What is the function of protein anchor?
Site of many proteins involved in transport, bioenergetics and chemo taxis
What is energy conservation?
Site of generation and use of the proton motive force.
What is the difference between gram positive and gram negative bacteria?
Gram positive bacteria have a thick layer of peptoglycans
Gram positive bacteria have a thick or thin peptidoglycan layer
Thick
Why are teichoic and lipoteichnoic acids important?
Serotyling
Facts of teichoic acid
Found in gram positive bacteria Impact a negative charge on bacteria Binds Mg2+ May be bound to membrane lipids Contain ester linkages to other sugars and D- alanine Involved in adherence to host tissue.
Teichoic acids contain
Acidic polysaccharides containing glycerol phosphate or ribitol phosphate
Peptidoglycan layer is known as
Murein
Importance of peptidoglycan layer
Critical for resistance to osmotic pressure
Hydrophilic nature provide resistance to some hydrophobic compounds.
Very important target for antibiotics
What is the chemical structure of peptidoglycan ?
N- acetylmuranic
Diaminopimelic acid
Repeating structure
A lipopolysachharide molecule that is released from the outer membrane of gram negative bacteria cell walls and causes the symptoms of the bacterial infection is called
Endotoxin
The chromosome in prokaryotes are located within
Nucleoid
Name a bacteria that lacks a cell wall
Mycoplasma
What shape does vibrio app have
Curved rod
What shape does corynebacterium have?
Club shaped
What shape does clostridium have
Spore forming rod
Functions of cell wall
Osmotic protection, solute transport, electron transport, electrochemical gradient/ ATP synthesis, motility.
Bacteria have which ions in their cytoplasmic membrane ?
Mg and ca2t
Core polysaccharide for endotoxins
Glu, gal. Hep,,KDO,GLUCOSAMINE
Gram negative envelope.
Outer membrane has pores formed by porin proteins large enou to diffuse trisaccharides..
Outer membrane can exclude large compounds .e.g vancomycin
LPS outer membrane
Oligosaccharide O side chain, core provides resistance to hydrophobic compounds. (Base for enteric bacteria)
DAP linkage is mostly seen in which category of bacteria ?
Negative
Peptidoglycan layer is porous or non porous?
Porous
Perisplasmic space
The space between the cytoplasmic membrane and the outer membrane.
It contains numerous proteins
Contains a peptidoglycan layer
Virulence factor such as hyaluronidase, b lactamse
Grain stain order
Crystal violet,gam iodine,decoloriser, safinin red
Mycobacterial cell envelopes
Lipid rich cell wall Acid fast Slow growth Resistance to penicillin and vancomycin Clumping q
Two bacteria that lack cell wall are
Mycoplasma and chlamydiacea such as chlamydia, chlamydophilia,
Mycoplasmas
Single membrane contains sterols, which are important for ridity
Related to gram positive bacteria
Smallest free livi f bacteria
Chlamydiaceae
Two membranes
Some genes for peptidoglycan synthesis found in genome
Obligate intracellular parasites
Non replication intracellular body,
Initial phase
Cells enlarge , metabolic activity increases
Exponential phase
Rapid multiplication, bacteria are susceptible to antibiotics
Stationary phase
Slow multiplication, some cells die,synthesis of Dana continues to some level, smaller cells appear
Decline
Decrease of the umber of viable cells due to lack of nutrients decrease in ph, accumulation of toxins
Growth of microbial populations
Binary fision( 30 minutes),DNA replicates, cell elongates then divides (60 minutes) , population doubles with each generation(90min),exponential growth ( 120 minutes)
Obligate aero best
Only aerobic conditions, presence of catalase and superoxide dismutase allows toxics form of oxygen. To be neutralised
Facultative anaerobes
Both aerobic and anaerobic growth, growth is excellent when oxygen is present
Obligate anaerobes
Only anaerobic growth, ceases in presence of oxygen, lack enzymes that allow tolerance to oxygen
Microaerophiles
Only aerobic growth,oxygen required in low concentrations
Hyperthermophiles
70- 105
Mesophiles
15- 45
Psychophiles
-5 - 15
Bacterial genome is composed of one circular chromosome
4-5 MB long
Contains double stranded molecules of DNA arranged in circular form
Condenses by supercoiling and looping into a dense,y packed nucleiod body,
Plasmids
Plasmids are circular DNA molecules present I. The cytoplasm of bacteria
Capable of autonomous replication
Can transfer genes to each other
Present in yeast
Transformation
Transfer of genetic information through the activity of DNA .
Experiment for transformation
Griffith expirement with mice
Bacterial transformation
DNA binds to the surface of a component cell and is cleved into fragment of about 15 mb
Natural transformation
Recipient cell has enzymatic machinery for DNA import
Artificial transformation
Damage to recipient cell walls allow donor DNA to enter cells.m
Electroporation
Mix donor DNA with recipient bacteria an subject to very brief high voltage
Lipofection
Used to transform cells of animals yeast plants and bacteria
Bacterial conjugation
Is genetic recombination in which their is a transfer of dnafrom a living organism to a recipient bacterium . Often using a sex pilus
3 conjugation process
Ft conjugation
HFr conjugation
Resistance plasmid conjugation
Two types if transduction types
Lyric and lysogenic
Transposon
Are transposable. Genetic elements that carry one or more other genes in addition to those which are essential for transposition