Gram Negative Bacteria Flashcards
What five types of Proteobacteria did we go over in lecture?
- Pseudomonads
- Enteric Bacteria
- Vibrio
- 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
- kidney
- small bowel
- bladder
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.
