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Flashcards in Gram Negative Bacteria Deck (21):

What five types of Proteobacteria did we go over in lecture?

- Pseudomonads
- Enteric Bacteria
- Spirelia
-Gliding Myxobacteria


Give a brief description of characteristics that apply to all of the microorganisms belonging to Pseudomonas and the Pseudomonads.

- straight or curved rods with polar flagella
- chemoorganotrophs
- obligate aerobes
-nutritionally versatile
- ecologically important organisms in water and soil
- some species are pathogenic
- includes human opportunistic pathogens and plant pathogens


Give an example of pathogenic pseudomonas.
L> animal and plant

- Pseudomonas aeruginosa
L> infections of urinary and respiratory tract
L> infections of burn wounds
L> lung infections in people suffering with cystic fibrosis
L> resistant to antibodies ( R Plasmids)
-Other pseudomonas species:
L> plant pathogens
L> yellow lesions of dead tissue
L> hypersensitivity response in tobacco (prevents further spread of infection)


Explain bioremediation wtr Pseudomonas

- they are capable of breaking down many compounds to non toxic compounds
- includes those that are not naturally occurring.
-pesticides, dyes, heavy metals and oil


Give a brief description of the characteristics of Enteric Bacteria.

- relatively homogenous phylogenetic group including E. coli
- facultative aerobes: respiration, ferments sugars producing a mixture of acids, H2 and CO2
- may be motile
- Nonsporulating rods
-possess relatively simple nutritional requirements


Enteric Bacteria:
- E. coli?
- Salmonella and Shigella?

- universal inhabitants of intestinal tract of humans and warm blooded animals
L> may synthesize vitamins for host
L> some strains are pathogenic such as O157:H7
- Closely related to Escherichia and is usually pathogenic


Enteric Bacteria:
- what are the different pathotypes?

- brain
- bloodstream
-large bowl
-small bowel


Vibrio Bacteria:
- describe their basic characteristics.
L> example of a well known human pathogen (Think of dirty London)

- cells are motile, straight or curved rods
- facultative aerobes/fermentative metabolism
-most inhabit aquatic environments (fresh water or marine)
- Vibrio cholerae causes cholera in humans
- some are capable of light production: bioluminescence, caralyzed by luciferase, regulation is mediated by population density (quorum sensing).


Vibrio Bacteria:
- Describe a species that is bioluminescent.

- Vibrio fischeri
- emits light
- associated with fish (light organ develops when colonized by bacteria..Flashlight fish)
- symbiotic relationship: host provides nutrients and shelter, luminescence can be used for communication and to hide the host from predators below.
ex2: Bobtail squid


Vibrio Bacteria:
- describe the biochemistry behind bioluminescence.

-requires enzyme luciferase, long chain aliphatic aldehyde (dodecanal (RCHO)), flavin mononucleotide (FMN) and oxygen

FMNH2 + O2 + RCHO --Luciferase--> FMN + RCOOH + H2O +Light


Vibrio Bacteria:
- Describe Quorum sensing

-in low bacterial numbers there is a low concentration of auto inducer and expression of specific genes is down regulated
- in dense bacterial populations there is a high concentration of auto inducer and expression of specific genes is up regulated


Vibrio Bacteria:
- Explain the regulation of bioluminescence via quorum sensing.

- luciferase only expressed when cells are at HIGH DENSITY
-this is achieved in a light organ
- Bacteria produce an autoinducer (homoserine lactone) -> diffuses out of the cell
- In sea water: Bacterial population density is low, HSL concentration is low, LuxR represses expression of LuxI, No HSL produced, no luciferase produced
- In the light organ: Bacterial population density is high, HSL accumulates in cytoplasm, Lux operon activated, Luciferase produced, more HSL is produced amplifying the signal


What are the morphologically unusual proteobacteria?

- Spirilla
L> Bdevellovibrio
L> Campylobacter and Helicobacter


Spirilla: Bdevellovibrio
L> Describe them.

- prey on other bacteria
- small size
- small genome
- highly motile
-obligate aerobes
- widespread in soil and water, including marine environments


Spirilla: Bdellevibrio
L> Describe the lifecycle of Bdellevibrio bacteriovorus

- attachment and penetration OM of host
L> resides in periplasm, breaks down peptidoglycan, assimilates organic compounds from the prey cytoplasm
- Bdellevibrio elongates without dividing
- cell division occurs once nutrients are used up: filament divides, differentiation into motile forms, Bdellevibrio released.


Spirilla: Campylobacter and Helicobacter
L> describe them briefly (Shared characteristics and pathogenisis)

- motile
-microaerophilic: require O2 at lower than atmospheric concentrations (3-15%)
- most species are pathogenic to animals or humans
- Campylobacter: enteritis (bloody diarrhoea)
- Helicobacter: causes gastritis and peptic ulcers, can survive the acidic conditions of the stomach.


Gliding Myxobacteria:
- briefly describe gliding bacteria
- briefly describe myxobacteria

- typically either long rods or filaments, lack flagella but can move when in contact with surfaces
- Gliding bacteria, form multicellular structures (fruiting bodies), complex developmental life cycles, chemoorganotrophic soil bacteria, lifestyle includes consumption of dead organic matter or other bacterial cells.


Give an overview of gliding myxobacteria vegetative cells and myxospores.

- veg: simple, nonflagellated rods, lysis of other bacteria, use released nutrients
- Myxospores: nutrients depleted, vegetative cells aggregate, construct fruiting bodies, differentiate into myxospores, resistant to drying UV and Heat (less resistant than endospores)


Describe the lifecycle of Myxococcus xanthus.
( Gliding Myxobacteria)

- vegetative cycle --> swarming and aggregation -> mound of cells --myxospore and fruiting body formation-->Fruiting Body---> myxospores--->germination--->outgrowth---> vegetative cycle
**vegetative cells can be chemically induced to become myxospores.


Explain gliding motility in Gliding Myxobaceria.

- they have evolved several cell wall protein complexes (polysaccharides)
- proton-motive force and hydrolysis of ATP to drive motion
- cell movement drives rotation. Motors maintain fixed positions with respect to the substratum and push the cell body forward.


Give a brief overview of the phylogeny of Proteobacteria.

- major lineage (phyla) of bacteria
- includes many of the most commonly encountered bacteria
- most metabolically diverse bacteria
L> chemolithotrophy, chemoorganotrophy, phototrophy etc
- morphologically diverse
- divided into five classes: Alpha-, Beta-, Delta-, Gamma- and Epsilon-