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‘Old’ Eubacteria
Blessing Chirenje
Alice Wagner
Aquificae
• Oldest branch of
Bacteria.
• One class, one order
and fiver genera:
Aquifex and
Hydrogenobacter.
• Oxidize hydrogen,
thiosulfate, and sulfur;
O2 electron acceptor.
Aquificae
• Thermophilic;
associated mainly with
hot springs, sulfur pools,
thermal ocean vents.
• Chemolithotroph:
utilizes carbon dioxide
as sole source of
carbon; energy from the
oxidation of inorganic
compounds.
Aquificae
• Gram Negative Rod
• Form large cell
aggregates, containing
up to about 100
individuals.
• Genus Aquifex grows
best at 85°C and can
grow at temperatures
up to 95°C.
Aquifex aeolicus
Genome 1/3 of E. coli; reduced metabolic flexibility:
cannot grow on sugars, amino acids.
16% of coding sequences similar to archaeal genes.
Thermotogae
• Thermophilic; optimal
growth 80-90°C
• Found in geothermally
heated soils and marine
sediments.
• Gram Negative Rod
• Chemoorganotroph:
depends on organic
chemicals for energy
and carbon.
Thermotogae
• Cell wrapped in sheathelike outer membrane
(“toga”).
• Anaerobic; reduces cystine
and thiosulfate to hydrogen
sulfide.
• Metabolize carbohydrates:
glucose, sucrose, starch,
cellulose
• Functional glycolytic
pathway.
Thermotoga
T. subterranea strain SL1 was
found in a 70°C deep
continental oil reservoir.
T. Maritima consists of one
circular chromosome: 1,860,725
bp.
Varying amounts of salt and
oxygen tolerance.
81 Aracheal-like genes.* 24%
*Nature 1999, 399 (6734):323-9
Deinococcus-Thermus
•One class, two orders:
Deinococcales and
Thermales
•Three phylum of which
Deinococci is best studied
•Deinococci are spheres or
rod-shapped with distinct
16s rRNA
Deinococcus
• GPC or GPR ; resistant
to radiation, extreme
heat, extreme cold,
drying, vacuum of
space.
• Breakdown nuclear
waste and toxic
chemicals.
• Isolated from ground
meat, feces, air, fresh
water.
• Natural habitat
unknown.
Deinococcus
• Aerobic, mesophilic heterotrophs;
occur in clouds and rainwater and
which can spoil food.
• Highly resistant to gamma and Xrays:
– Very efficient DNA repair
system.
– D. radiodurans have 4-10 copies
of their DNA molecule. Most
bacteria have only one copy.
– Megaplasmid and small plasmid
chromosomes
Deinococcus
• Associated in pairs or
tetrads;
• Atypical GP cell wall
periplasmic space has
large amounts of
palmitoleic acid.
• D. radiodurans: radiation
1000X greater than
would kill a human.
• Latin: "strange berry
that withstands
radiation.
Thermus thermophilus
• Thermophilic
heterotrophs found in
warm water
environments especially
hot springs.
• Source of Taq
polymerase used in the
PCR:
– enables DNA to be
replicated in large
quantities.
Thermus thermophilus
• Gram-negative bacteria.
• Optimal growth
temperature of 48°C and
85°C
• Ribosomes and ribosomal
subunits do not disintegrate
when kept for longer
periods at 20°C'
• “Down-temperature”
evolution*
• Crystal structure of
homoisocitrate
dehydrogenase
*1999, University of Wisconsin, Board of Regents.
'Cell 102: 615-623 (2000)
Chlamydia
• The phylum Chlamydiae
has one class, one order,
four families and six
genera.
• They evloved about 2
billion years ago.
• Nonmotile, coccoid,
gram-neagtive.
• One of the smallest of
all bacteria; ~ 500 nm in
width, not much bigger
than the largest viruses.
Chlamydia
•Obligate Intracellular bacteria
with a unique developmental cycle
involving elementary bodies (EBs).
•Elementary bodies reorganize
into reproductively specialized
reticulate bodies (RBs) which then
change back to infectious
elemenatry bodies.
•Completely dependent on the host
for ATP.
Chlamydia
• Gram-negative-like wall
but lacks muramic acid
and peptidoglycan
• Use cross-linking of
outer membrane and,
possibly, periplasmic
proteins to achieve
osmotic stability
• Found mostly in
mammals and birds but
have been recently
isolated from spiders,
clams and freshwater
invertebrates
Chlamydia
Three recognized human
pathogens
– C. trachomatis - causes
chlamydia, a sexually
transmitted disease,
trachoma, an eye infection
that is a frequent cause of
blindness and other human
diseases.
– C. psittaci- causes psittacosis
in humans and infects many
other mammals as well.
– C. pneumoniae - a causative
agent of human pneumonia
Spirochetes
• The phylum has one class,
Spirochaetes, three families,
and 13 genera.
• Gram-negative,
chemoheterotrophic; long
flexibly helical coiled
bacteria.
• Most are free-living and
anaerobic, but can be
symbiotic, or parasitic.
• Distinguished by the
presence of flagella
running lengthwise
between the cell membrane
and cell wall, called axial
Spirochetes
•
•
•
The axial filament (a complex of
periplasmic flagella) lies in a flexible
outer sheath (outer membrane)
outside the protoplasmic cylinder
that houses the nucleoid and
cytoplasm; the function of the sheath
is essential, but unknown.
Flagellar rotation is responsible for
motility by an unknown mechnism
presumably by rotating the outer
sheath or flexing the cell for a
crawling motion.
Spirochete can move through very
viscous solutions though they lack
external rotating flagella.
Spirochetes
• Exceptionally diverse ecologically and grow in habitats
ranging from mud to the human mouth.
• Ecologically diverse:
– Spirochaeta are free-living, and grow in anaerobic and
sulfide-rich fresh water and marine environments.
– Leptospira is both pathogenic and saprophytic, can
occupy diverse environments, habitats and life cycles.
– Treponema includes the caustive agent of syphillis (T.
pallidum)
– Borrelia includes the caustive agent of Lyme
disease (B. burgdorferi)