1 Bacterial Properties Flashcards
Q: Describe bacteria. Size? Multi/unicellular? Organelles? Hap/diploid? Some have?
A: small and unicellular
no internal organelles (no chloroplasts, nucleus, ER, mitochondria)
Haploid
Some have flagella
Q: What is gram stain used for? How? (4)
A: technique that distinguishes between two kinds of bacterial cell wall- Gram-negative or Gram-positive bacteria
Bacteria are stained with a violet dye and iodine, rinsed in alcohol, and then stained with a red dye
Q: Describe the 2 types of bacteria that the gram stain distinguishes.
A: Gram positive bacteria: Peptidoglycan in cell wall retains dye
High peptidoglycan = deep violet
Gram negative bacteria: Dye is lost from thinner peptidoglcan
The cells absorb counterstain making them appear pink
Q: Describe gram positive cell wall structure? (4)
A: You get the cytoplasmic membrane with a THICK LAYER of peptidoglycan on top (which retains the dye and stains DEEP VIOLET)
have embedded channel proteins
one membrane
no LIPOPOLYSACCHARIDE present (LPS)
Q: Describe gram negative cell wall structure? (5)
A: have TWO MEMBRANES (inner and outer)
peptidoglycan is sandwiched between the inner membrane and the outer membrane
Both membranes have embedded channel proteins
Outer Membrane - composed mainly of LIPOPOLYSACCHARIDE (LPS) = PAMP
many have injectisome structure
Q: How do extracellular and intracellular bacteria vary?
A: Extracellular bacterial pathogens do not invade cells and proliferate instead in the extracellular environment eg blood
intracellular= invaginate the membrane of a host cell and gains entry into the cell - they remain in a membrane bound vesicle (endosome) and find ways of avoiding being lysed
Q: What are 3 methods for pathogens to survive in the host cell?
Which pathogens are examples of these methods? (3,2,1)
A: Prevent Fusion with Lysosomes - Salmonella, Mycobacteri and Chlamydia
Escape - Listeria and Shigella break down the vesicle and escape into the cytoplasm
Survive in Phagolysosome - Coxiella can just survive in the harsh environment inside a phagolysosome
Q: Give examples of extracellular pathogens. (4)
A: Staphylococcus
Streptococcus
Yersinia
Neisseria
Q: What are the salmonella surface structures and what do they enable? (2)
Relationship?
A: motility- flagellum
invasion- injectisome/ Type III Secretion System
share common evolutionary origin
Q: Describe salmonella’s use of injectisome/Type III Secretion System. (5)
A: Instead of making a flagellum, a bacterium can make this needle shaped structure which allows effector proteins to be injected into the host cell through translocase (a translocon which inserts into the plasma membrane of the host cell)
proteins are injected -> stimulate actin polymerisation which drives membrane ruffling and internalisation of the bacterium
Q: How does the flagellum structure allow movement? Organised as? (2)
A: Flagella allows the propulsion of bacteria through fluids - they are filamentous structures and they rotate and are organised as a series of rods and filaments
Q: Apart from the injectisome, describe another example of manipulation of actin by a bacterial pathogen. (4) Result? Known as?
A: Listeria
It breaks out of the vacuole (produces specific proteins to do so)
It then assembles/polymerises actin at one pole of the bacterial cell
This polymerisation of actin generates force which propels the bacterium through the cytoplasm (forms protrusion-> engulfment by neighbouring host cell)
This leads to the spread of the bacterium
These streams of actin are known as COMET TAILS
Q: What can listeria cause? in? (3)
A: causes food poisoning and more serious disease in immunocompromised, elderly and pregnant women
Q: What are the 3 main ways bacteria exchange genetic material? Allow? Overall name?
A: Horizontal Gene Transmission which allows accessory genes to be acquired
Transformation
Transduction
Conjugation
Q: Describe transformation as a method of bacteria genetic material exchange (horizontal gene transfer).
A: Sucking up DNA from outside
They can recognise naked DNA (e.g. from the lysis of other bacteria)
They have transport mechanisms which allow uptake of this DNA and incorporation into the bacterial chromosome
Q: Which 2 pathogens can gain genetic information via the transformation method?
A: Neisseria and Streptococcus
Q: Describe transduction as a method of bacteria genetic material exchange (horizontal gene transfer).
A: When bacteriophages invade bacteria, it replicates its DNA in the bacterium and cuts the bacterial DNA into small pieces
Some bacterial DNA may be packaged into the phage heads
New phage particles are released
The phage particles injects the bacterial DNA from the previous bacterium it infected into the next bacterium.
Injected DNA may be incorporated into the bacterial chromosome
Q: What type of pathogens can gain genetic information via the transduction method?
A: Many Gram - and Gram + can do this
Q: What is a bacteriophage?
A: virus that infects and replicates within a bacterium
Q: What type of pathogens can gain genetic information via the conjugation method?
A: Many Gram - and Gram + can do this
Q: Describe conjugation as a method of bacteria genetic material exchange (horizontal gene transfer).
A: You get a physical bridge between bacteria which allows the transfer of a plasmid between the bacteria
Q: What are the 3 shapes/forms bacteria can take?
A: coccus= spherical
bacillus= rod-shaped
spiralli= spiral-shaped
Q: What does horizontally acquired DNA contribute to?
A: virulence
access to a wide variety of DNA
Q: What genome do acid-fast bacteria belong to? Characterised? (5) How are they identified?
A: genus Mycobacterium
- wax-like, nearly impermeable cell walls
- contain mycolic acid
- contain large amounts of fatty acids,
- waxes
- complex lipids
acid-fast stain = differential stain
Q: What follows a gram stain? (4) Popular option?
A: Culture and microscopy
Biochemical and serological tests
DNA techniques such as PCR (popular)
Sensitivities to antibiotics
Q: Name 5 gram negative bacteria and their associated disease. (4,2,1,1,2)
A: 1. Escherichia coli (EPEC - diarrhea, EHEC - produces toxin, dysentery and kidney failure)
- Salmonella (typhimurium - food poisoning, typhi - typhoid)
- Shigella (dysentery)
- Vibrio cholerae (cholera)
- Neisseria (meningitidis- meningitis, gonorrhoeae- gonorrhea)
Q: Name 3 gram positive bacteria and their associated disease. (5,3,4)
A: 1. Staphylococcus aureus (skin diseases, endocarditis, bacteraemia, joint diseases, pneumonia)
- Streptococcus pneumoniae (pneumonia, meningitis, otitis media)
- Streptococcus pyogenes (tonsilitis, necrotizing fasciitis, bacteremia, scarlet fever)
Q: What are mycobacteria identified by? Name 2 and their associated disease.
A: not identified by gram stain
- Mycobacterium tuberculosis (TB)
- Mycobacterium leprae (leprosy)
Q: What 5 things do bacterial pathogens need to be able to do?
A: Colonise (surface structures eg pili allow them to cling onto surfaces)
Persist (ability to avoid the host defences - deal with innate immune function)
Replicate (acquire nutrients needed for replication e.g. iron)
Disseminate within cells, tissues, between organs and hosts
Cause Disease - produce toxins that kill host cells - dysregulation of host immune responses
Q: What makes up the gene repertoire of a bacterium? (2)
A: core genes (40%) - most are involved in housekeeping functions
accessory genes (vary considerably between different strains)
Q: What is a pathogenicity island? Driver?
A: virulence properties are accessory genes acquired via horizontal gene transmission (often looks different to core genes
virulence properties of bacteria are frequently encoded in said islands/islets
main drivers of evolution of bacterial pathogens and their origin is usually unknown
Q: What 4 things have contributed to bacterial evolution? In what regard?
A: -massive source of genetic variation
- rapid generation time
- selective pressure (our immune system(
- approx 1000,000,000 years
=evolution (gives them properties that enable them to cause disease)
