bacterial diversity and growth Flashcards
taxonomy
the science of classification. Identifies the relationships between groups of organisms. Can be used to identify novel species.
taxa
categories of organisms
relatedness is a result of
evolutionary history or phylogeny
the three domain theory of classfication
originally based on physical difference by microscopy. Now done by genetics
prokaryotes
no membrane bound nucleus of organs
gram positive
purple and thick peptidoglycan retains the crystal violet
gram negative
thinner peptidoglycan doesn’t retain the stained is counterstains with safranin
operating into two groups is not enough
can be gram variable or indeterminate
how can we study non cultural bacteria
culture independent analyses: fluorescent oligonucleotide that binds specific DNA
–> hard: you have to know what you are looking for to design oligonucleotides
gram positive bacteria is further subdivided into
low G+C and High G+C based not he % of GC in genome
low G+C known as
Firmicutes
low GC content
30%- firmicutes
hight GC content known as
actinobacteria
high GC content
60-70% actinobacteria
firmicutes
lactobacillus, streptococcus, staphylococcus, bacillus, clostridium
lactobacillus and streptococcus are members of the lactic acid bacteria (LAB)
produce lactic acid during metabolism and tolerant to low pH
staphylococcus, bacillus and clostridium produce other acidic by products e.g.
butyric acid, propionic acid, acetic acid
lactobaccillus
- bacillus-rod shaped.
- variable in size
- imporntnat part of human gut flora
staphylococcus
- coccus-round
- medically important
- s.aureus- boils proidec toxins
- MRSA
- commensal- S.epidermidis
found in the nose and harmless skin bacteria
clostridium
- rod shaped
- forms endospores
- medically important
- C.tetani- tetnus
- C. botulinum
- C.difficile- hospita associated
streptococcus
- ‘twisted chain’
- coccus
- Divide on a single axis therefore the rrogenitorcells grow in pairs or chains
examples of high GC gram positives
actinomcyes
frank
streptomyces
actinmycetales the order of:actinomcyes
frank
streptomycin… have a similar appearance to
fungus–> originally thought to be fungi before DNA technology
frankia
filamentous, carry out nitrogen fixation in soils. Atmospheric N to ammonia
streptomyces
- from mycelium
- produce spores called conidia not same as endospores
- important producers of antibiotics
when do streptomycin produce antibiotics
during nutrient depletion therefore a survival mechanism for competition –> active against gram +ve and -ve bacteria and fungal infections
actinmyces
facultative anaerobes. Looks like fungal hyphae under microscope. Important for soil ecology
proteobacteria
gram negative bacteria
proteobacteria- gram negative bacteria is subdivided into
alpha, beta, gama, delta, epsilon
alpha
rhizobiales
rhizobiales: Bradyrhizobium/ Rhizobium
Bform symbiosis with plants and fix nitrogen to ammonia
beta
Neisseriales
Neisseriales: Neisseria
diplococci. medically important - meningitis- carried by 95% of pop
- -> gonorrhea
gamma
Enterobacteriales
enterobacteriales
shigella
escherichia
salmonella
enterobacteriales: shigella and salmonella
responsible for serious good poisoning
enterobacteriales escherichia
common inhabitant of intestinal tract but uncommon pathogen
epsilon
Campylobacterales
campylobacterales
campylobacter and helicobacter
campylobacterales: campypylobacter
highly motile bacillus, curve- food born disease e.g. C.jejuni
campylobacterales: helicobacter
has multiple flagella. causes stomach ulcers e.g. H pylori
which is the most common proteobacteria (gram negative)
Y-proteobacteria- contains many human pathogens
why is so much known about the gram negative proteobacteria and gram positive firmicutes?
they are easily cultured and grown in labs
what needs to be studied to classify bacteria
the study of 16S rRNA.
FISH- fluorescent in situ hybridisation.
Different coloured oligonucleotides match diff 16s rRNA sequences. can identify the complexity of a bacterial group
16s rRNA gene is
common in all bacteria, but varies slightly in its sequence between related species
binary fission
a kind of asexual reproduction- fly grown parent cell splits into two halves- producing two new cells
process of binary fission
- cell elongation
- septum formation
- completion of septum; formation of walls and cell separation
B.subtilis
no cell wall constriction in binary fission
Caulobacter
no septum formation in binary fission
obligate aerobes
bacteria can only grow in oxic zones (oxygen rich)
anaerobes
can only grow in anoxic zones
facultative aerobes
can grow in both oxic and anoxic conditions–> however higher conc of bacteria in oxygen rich areas
microaerophiles
prefer to grow in more oxic zones
aerotolerant
has no preference to oxic or anoxic environments
segregation of genomes
facilitated by proteins MinC, D and E.
-MinE pushes C and D to the poles and acts as a signal for FtsZ
what protein is essential in cell morphology
MreB–> thought to give rod shape and give bacterial cytoskeleton. Coccoid cells do not have MreB suggesting that this the default shape for a bacterium
both mass and cell number increases as
generation time increases- exponential growth
what is the most important factor affecting growth
temperature
e. g. as temp increases so does growth rate, until maximal rate and then protein denaturation; collapse of cytoplasmic membrane and thermal lysis
- -> due to ENZYMES having an optimum temo
diff bacteria have different optimal temps
e.g. some grow best at temps below zero and others temps above 100
psychrophiles
grow best at 4 degrees, but can grow at temps below 0. e.g. Polaromonas vacoulata
mesophile
39 degrees e.g. E.coli
Hyperthermophiles
106 degrees e.g. Pyrolobus fumarii
