bacteria Flashcards
first living things
anaerobic, heterotrophic, and bacteria
traits all organisms got from universal common ancestor
DNA( universal genetic material- same nucleotides and double helix)
DNA replication to reproduce (semiconservative with same enzymes like helicase and polymerase)
Domains
domain bacteria (most primitive, branched off first), domain archaea (live in old ways like extreme environments)(archaeobacteria) domain eukarya
bacterial ancestral traits
no histones,
single main chromosome
bacteria cellular structures
Nucleoid Plasmid Ribosomes Pili Capsule Flagella
nucleoid
main chromosome
plasmid
small circular DNA trading cards, extra copies of important genes
pili
projections of cell membrane, how plasmids are passed
capsule
gelatinous coating
flagella
with no microtubules/basal body
what type is bacterial replication
asexual, rapid, only differences are produced with mutations
bacterial replication process
Origin duplicated
DNA helicase unwinds DNA
DNA polymerase complex called replisome
2 replication forks move opposite directions
Topoisomerase cuts DNA to avoid over-coiling
prokaryotic fission process
Origins attach
Cell elongates-through adding phospholipids to elongate space between origins
Cytoplasmic division
No random assortment
how to get genetic variation in bacteria
lateral genetic exchange- giving genes to friends and neighbors, not genetically related, not linear
advantages to lateral gene transfer
rapid passing of new phenotypes
conjugation
bacteria to bacteria via tube, direct contact
transduction
virus introduces new DNA, injects bacterial DNA by accident
transformation
uptake of DNA through cell membrane (plasmids)
gaining new phenotypes by the environment through the cell membrane
famous transformation experiment by Griffith
infects mouse with rough and smooth pneumonia. Lives with rough, but dies with smooth because it protects from immune system. Killed smooth strand put in with rough strands, and mouse dies because the smooth transfers plasmids to rough bacteria
bacterial conjugation process
. Donor cell (F+) gives a plasmid to recipient cell
F+ fertility plasmid directs sex pilus formation (forms tube)
Conjugation tube joins cytoplasm
Relaxase nicks donor plasmid (cuts covalent bond in backbone and then unwraps helix)
One strand of plasmid nucleotides moves into recipient cell
Both strands replicated back into double helix
bacterial mutation rates
very high due to reproduction rates
identifying/classifying bacteria
Characteristics that are considered
a) Shape
b) Gram staining ( + or -)
c) Metabolism
d) Gene sequencing
gene sequencing
causes re-structuring of classification
shows genetic divergence from all other life shortly after emergence of first cell
shape cocci
round
shape bacilli
rod
shape spirilli
spiral
cell arrangements diplo
pairs
cell arrangements strepto
chains
cell arrangements staphylo
bunches
gram staining
used when bacteria is hard to treat, can be positive or negative
gram staining positive
picks up stain so turns violet, want positive because most antibiotics can get to cell, lots of peptidoglycan in cell wall
down side of gram staining positive
form endospores
gram staining negative
stains red, less peptidoglycan
outer membrane- resistant to drugs, membranes make it hard to get antibiotics to the cell
Peptidoglycan =
sugars cross-linked by peptides
Chemoheterotrophs –
E from bonds, organic C
parasites, saprobes, decomposers
Chemoautotrophs –
E from bonds, C from CO2
thermophilic bacteria, some of most primitive. Energy from iron or sulfur compounds (volcanos)
Photoautotrophs –
E from sun, C from CO2
cyanobacteria, stromatolites
what does gene sequencing show?
Shows bacteria diverged from all other lineages shortly after first cells appeared, made it why we needed domains
example of an analogous structure for eukaryotic and prokaryotic
flagella
bacteria flagella
ATP run protein motor,
has a hook & filament
Archean flagella
same design as bacteria, ATP run protein motor with a hook & filament, but different proteins
eukaryotic flagella
is covered in a membrane and has microtubules with basal body
Signal transduction –
extra cellular signaling molecule binds to receptor and initiates response
taxis
innate behavioral response to move toward or away from directional stimulus
4 types of taxis
magnetotactic (magnetic fields)
phototactic (light)
thermotactic (heat)
geotactic (gravity)
kinesis
non-directional change in activity in response to a stimulus (bad feeling, need to move, don’t know where just move)
quorum sensing
intercellular communication Bacteria use signaling molecules (specific to species) to sense bacterial cell density. inducible operon
in quorum sensing what happens with sufficient signal molecule concentration
triggers communal response
gene expression activated,
proteins produced & excreted
QS enables bacteria to
to co-ordinate their behaviour. As environmental conditions often change rapidly, bacteria need to respond quickly in order to survive. ex; bacteria in body to escape immune system,
virulence bacteria
Virulence factors are molecules expressed and secreted by pathogens that enable them to achieve:
colonization of a niche in the host
Immunoevasion- evasion of the host’s immune response
Immunosuppression- inhibition of the host’s immune response
Entry into and exit out of cells
