bacteria lecture 3 Flashcards
bacteria have inclusion bodies what are these for
energy storage
3 functions of a the plasma membrane of bacteria
- permeability barrier to protect the cell from losing nutrients
- protects from being harmed by environmental toxins/waste
- large surface area for photosynthetic and respiratory functions
Bacterial cell walls are made of peptidoglycan.
what are the 2 main types of bacteria cell walls indicated by the Gram stain technique
- Gram positive=peptidoglycan>lipids
- purple
- thick cell wall made of peptidoglycan - Gram negative=lipids>peptidoglycan
- pink
- thin peptidoglycan layer between inner and outer membrane (lipid bilayer on top and under)
3 types of appendages on the cell surface of bacteria
- pili
- fimbriae
- flagella
pilus
long hair-like structure used for attachment or to form a mating bridge between cells for exchange of genetic material e.g. conjugational plasmids
fimbriae
shorter versions of pili used for attachment to substrate
flagella
log, whip-like appendages which rotate in a corkscrew motion to propel bacteria forward
capsule
- surrounds cell wall
- assists with attachment to surfaces and protection again dehydration/ host’s immune system
endospore 4 characters
- produced when under environmental stress
- consists of bacterial DNA, small amount of cytoplasm and thick protective coat
- resistant to UV radiation, desiccation, high temp and chemicals
- lie dormant until favorable conditions arise
binary fission
mother divides into 2 identical daughter cells
what protein is essential for binary fission
protein FtsZ (Filamenting Temperature Sensitive mutant Z)
4 steps of binary fission
- DNA replication
- DNA segregation
- infolding of the cell membrane
- synthesis of new cell wall
bacterial are successful for 2 reasons
- rapid growth rate
2. ability to transfer DNA through horizontal gene transfer (much quicker then going via generations)
4 main cell shapes
- spherical=cocci
- rod shaped=bacilli
- spiral=spirilli
- filamentous=actinomycetes
2 largest phyla of bacteria
- firmicutes=gram+
2. proteobacteria=gram-
bacteria that use radiant energy =
phototrophs
photo-autotrophs use
sunlight and CO2
if oxygen is present what kind of respiration do bacteria undergo
aerobic cellular respiration
if oxygen is absent what kind of respiration do bacteria undergo
fermentation
what are the 2 broad environmental importance of bacteria
- they are decomposers and fixers
2. symbiotic relationships
decomposers
breakdown dead organisms and plants thereby returning elements to the ecosystem
fixers?
converting inorganic compounds to forms that can be used by other organisms
Nitrogen cycle
- nitrifying and denitrifying bacterial interconvert N-containing compounds
- convert N2 to NH3 which can be used by other microbes
carbon cycle
- carbon-fixers such as autotrophs convert CO2 to organic compounds
- whilst others oxidise organic compounds and release CO2
2 types of symbiosis (+short def)
- mutualism-both partners benefit
2. commensalism-one partner may benefit without harming the other (rare)
3 examples of mutualism
- Rhizobium bacteria and legume roots
- bacteria supply N to plant
- plant supplies organic carbon - cellulase-producing bacteria that live in the digestive systems of cows
- colonies of bacteria in human intestinal tract where they assist with digestion and produce vitamins (especially B12 and K) which the body cannot produce itself
bacterial biofilms
-survival mechanism as it provides protection against unfavourable environmental conditions.
bacterial biofilms contribute to a negative thing
development of resistance against chemicals and antibiotics that are usually used to control them
how does HGT affect evolution
the idea of a single ancestor giving rise to separate “branches” forming the “tree of life” may have to be revised to a network of life with interlinked”‘branches” where microbes have exchanged genes
what types of genes are transferred
genes that give the organism immediate selective advantage over its competitors
3 main methods of HGT
- transformation
- transduction
- conjugation
HGT via transformation
bacterial natural take up, or chemically induced to take up, bits of DNA from the environments and integrate it into their genome
HGT via transduction
bacteriophages can infect bacteria and carry DNA from one host to another
bacteriophage
bacterial virus
HGT via conjugation
bacterial can mate with one another and transfer DNA from cell to cell via pili
example of HGT
MRSA
Methicillin-Resistant-Straphylococcus aureus
-bacteria is resistant to a wide range of bacteria
-occurs widely in hospitals
