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Bacteria and Archaea

Chapter 27

Laurie Gardner

on 16 February 2011

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Transcript of Bacteria and Archaea

Bacteria and Archaea Structural and
Functional Adaptations
Contribute to Prokaryotic Success cocci--spherical prokaryotes
pairs (diplococci)
chains (streptococci)
bacilli--rod shaped prokaryotes
usually singular
some chains (streptobacilli)
spiral--spiral prokaryotes
comma like to long coils Cell-Surface Structures A key feature of nearly all prokaryotic
cells is th cell wall, which maintains cell
shape, provides physical protection, and
prevents the cell from bursting in the
hypotonic environment. Gram Stain classifies many bacterial species into two groups:
the stain stains the peptidoglycan of the cell wall Gram-negative bacteria tend to be more resistant than gram-positive. a cell wall of many prokaryotes
if covered with a capsule some prokaryotes stick to their
substrate or to one
another by means of fimbriae motility about half of all prokaryotes are capable
of directional movement Internal and Genomic Organization some prokaryotic cells do have specialized membranes that perform metabolic functions. Reproduction and Adaptation Prokaryotes can reproduce quickly in a
favorable environment by binary fission. If reproduction continues unchecked
a single prokaryotic cell could give rise to a colony outweighing the Earth in 3 days!!! Reproduction in prokaryotes draws attention to 3 key features:
they are small
they reproduce by binary fission
they have short generation times Rapid reproduction, mutation, and gentic recombination promote genteic diversity in prokaryotes rapid reproduction and mutation genetic recombination transformation and transduction prokaryotes reproduce by binary fission so at
first their diversity may seem puzzling but their rapid reproduction.
Any insertions, deletions or base-pair substitutions equal large changes.
EX: a single E.coli can produce up to 9 million mutations per day in a human host. genetic recombination in bacteria comes from either:
conjugation transformation involves the alteration
of genotype and possibly the phenotype
by the uptake of foreign DNA from it's
surroundings. transduction (specific to phages) is a type of horizontal genes transfer and results from accidents that occur during the phage reproductive cycle. conjugation and plasmids in conjugation genetic material is transferred between two bacterial cells that are temporarily joined the ability to form sex pili and donate DNA during conjugation results form the presence of a particular piece of DNA called the F factor R plasmids are resistance genes carried by some plasmids.
Another form of pseudo-resisitance is found in the endospores. Diverse nutritional and
metabolic adaptations have evolved in prokaryotes prokaryotes can be categorized by their nutrition the role of oxygen
in metabolism obligate aerobes--
use O2 for cellular respiration and cannot grow w/o it
obligate anaerobes--
are poisioned by O2, some live exclusivesly by fementation and some by anaerobic respiration
facultative anaerobes--
use O2 if present but can carry out fermentation or anaerobic respiration also nitrogen metabolism nitrogen is essential for the production of amino acids and nucleic acids in all organisms prokaryotes can metabolize nitrogen in a varitey of ways through a process called nitrogen fixation metabolic cooperation heterocytes
cells that carry out only
nitrogen fixation cooperation b/w prokaryotes allows them
to use environmental resources they could not
use as individual cells this biofilm consists of numberous bacterial species that form on tooth surfaces--dental plaque Molecular systematics is
illuminating prokaryotic phylogeny formerly systematists based prokaryoteic taxonomy
on shape, motility, nutritional mode, and response to
Gram stain This is helpful for quickly culturing and identifying bacteria however it does not reveal clear
evolutionary phylogeny this phylogenetic tree based on molecular data highlights the relationships b/w the major prokaryotic groups Archae Bacteria Archae share certain traits w/ bacteria and others with eukaryotes extremophiles
extreme halophiles
live in highly saline solutions
extreme thermophiles
moderate condition archae include
use CO2 to oxidize H2 to form energy
release methane as a waste
poisioned by O2 p. 568-569 all major groups of bacteria proteobacteria
gram-positive bacteria prokaryotes play crucial
roles in the biosphere chemical recycling ecological interactions prokaryotes are so important
to the biosphere, if they were
to disappear, the prospect of survial
for many other species would
be dim. chemoheterotrophic
prokaryotes functions as
decomposers, breaking down corpses, dead vegetation, and waste products unlocking a supply of carbon,
nitrogen and other elements symbosis--living together--
prokaryotes are small, and they often
form symbiotic relationships with larger
organisms. The larger organism is the
host and the smaller is the symbiont.
mutalism--an ecological interaction in which both benefit. commensalism--
when one species is benefits but
the other species is not harmed or
helped in a significant way. parasitism--
when a parasite eats the cell contents, tissue, or body fluid of its host, usually harming but not killing the host. parasites that cause diseases
are called pathogens Prokaryotes have both
harmful and beneficial impacts
on humans
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