Chemoautotrophs and photosynthetic eubacteria
Transcript of Chemoautotrophs and photosynthetic eubacteria
troph = nourishment
auto = self
chemo = chemical
chemoutotrophs
derive energy from chemical reactions
synthesize all necessary organic compounds from carbon dioxide
use inorganic energy sources, such as hydrogen sulfide, elemental sulfur, ferrous iron, molecular hydrogen, and ammonia
They can be also called as chemolithoautotrophs .
Most chemoautotrophs
are bacteria or archaea that live
in hostile environments such as deep
sea vents, active volcanoes and are
the primary producers in
such ecosystems
A unique characteristic of these
chemoautotrophic bacteria is that
they thrive at temperatures high
enough to kill other organisms
use inorganic reduced compounds as a
source of energy
This process is accomplished through
oxidation and ATP synthesis
Most chemolithotrophs are able to fix
carbon dioxide (CO2) through the Calvin
Cycle, a metabolic pathway in which
carbon enters as CO2 and leaves
as glucose
Chemolithotrophy: Energy from the Oxidation of Inorganic Electron Donors
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Carry out respiration by coupling the
oxidation of an inorganic compound
to the reduction of membrane-bound
electron carriers:
most ATP produced by oxidative
phosphorylation
inorganic electron donor
protons pumped out
proton motive force
ATP synthesis
e– electron transport chain
sulfur oxidizers
nitrifying bacteria
iron oxidizers
Hydrogen oxidizers.
Anammox Bacteria
ATP has a free energy of -31.8
kJ/mol
2H2 + 02 2H20 (1)
2 H2 + C02 <CH20 > + H20 (2)
6H2 + 202 + CO2 <CH20> +5 H20 (3)
Hydrogen Bacteria
Ralstonia eutropha is a gram-negative soil bacterium of the
betaproteobacteria class
Many species of nitrifying bacteria
have complex internal membrane
systems that are the location for key
enzymes in nitrification: ammonia
monooxygenase which oxidizes
ammonia to hydroxylamine,
and nitrite oxidoreductase, which
oxidizes nitrite to nitrate.
Nitrifying bacteria are widespread in the
environment, and are found in highest
numbers where considerable amounts of
ammonia are present (areas with
extensive protein decomposition, and
sewage treatment plants).
They thrive in lakes and streams with high
inputs of sewage and wastewater
because of the high ammonia content.
Nitrification in nature is a two-step oxidation process of
ammonium (NH4+ or ammonia NH3) to nitrate (NO3
-)
catalyzed by two ubiquitous bacterial groups. The first
reaction is oxidation of ammonium to nitrite by
ammonium oxidizing bacteria (AOB) represented
by Nitrosomonas species. The second reaction is
oxidation of nitrite (NO2-) to nitrate by nitrite-oxidizing
bacteria (NOB), represented by Nitrobacter species.
Ammonia oxidation: It is a complex
process that requires several enzymes,
proteins and presence of oxygen. The
key enzymes, necessary to obtaining
energy during oxidation of ammonium
to nitrite are: ammonia
monooxygenase (AMO) and
hydroxylamine oxidoreductase (HAO)
In anoxic ammonia oxidation, the nitrifying bacteria can use ammonia
and nitrite as electron donors, a process called nitrification. The
ammonia-oxidizing bacteria produce nitrite.
Nitrite produced in first step autotrophic nitrification is oxidized to nitrate by nitrite oxidoreductase (N0R)(2). It is a membrane-associated iron-sulfur molybdoprotein, and is part of an electron transfer chain which channels electrons from nitrite to molecular oxygen. The molecular mechanism of oxidation nitrite is less described than oxidation ammonium.
The ammonia-oxidizing bacteria produce nitrite which is
then oxidized by the nitrite-oxidizing bacteria to nitrate.
Nitrosococcus
NH3
NO2–
Nitrobacter
NO2–
NO3–
No single bacterium oxidizes ammonia
all the way to nitrate.
Nitrobacter
Nitrobacter is a genus of mostly rod-shaped, gram-negative, and chemoautotrophic bacteria. Nitrobacter plays an important role in the nitrogen cycle by oxidizing nitrite into nitrate in soil
Nitrosomonas
Nitrosomonas is a genus comprising rod shaped chemoautotrophic bacteria. This bacteria oxidizes ammonia into nitrite as a metabolic process. Nitrosomonas are useful in treatment of industrial and sewage waste and in the process of bioremediation
“White Streamers”
color due to sulfur granules in cells
Fe Oxidation at low pH
The pH effect on Fe+2 concentrations is reflected in the energy yield:
Fe+2 + O2 + H+ Fe+3 + H2O
Thiobacillus ferrooxidans, an acidophilic iron-oxidizer, pH optimum for
growth of 2 to 3
Contribute to formation of acid mine drainage.
Thiobacillus-type [rods] in yellow
floc from acid water
The iron bacteria are chemolithotrophs that use ferrous iron (Fe2+) as
their sole energy source.
Most iron bacteria grow only at acid
pH and are often associated with
acid pollution from mineral and coal
mining.
Extensive development of
insoluble ferric hydroxide in a
small pool draining a bog in
Iceland. Iron deposits such as this
are widespread in cooler parts of
the world and are modern
counterparts of the extensive bog
iron deposits of earlier geological
eras
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NH4+ + NO2
- N2 + 2 H2O
Anammox - Anaerobic ammonium oxidation
Brocadia anammoxidans
Brocadia anammoxidans
"Candidatus Brocadia anammoxidans" is a bacterial member of the
order Planctomycetes and therefore lacks peptidoglycan in its cell
wall, has a compartmentalized cytoplasm.
Anammox bacteria:
Planctomyces group
Enrichment culture of the anammox
bacterium Kuenenia stuttgartiensis
Eubacteria, known as "true bacteria," are prokaryotic
(lacking nucleus) cells that are very common in
human daily life.
They have a single strand of DNA. Eubacteria Lack a nuclear membrane. Eubacteria have phili which help transfer
DNA. The cytoplasm is filled with ribosomes. Eubacteria lack a nuclei or nucleus . Some Eubacteria have a flagella. A tail like
structure to help them move. Eubacteria have a plasma membrane to
hold the insides of the cell in place. They are enclosed by a cell wall that
provides as a rigid wall to keep the cells shape.
Phototrophic bacteria are a group of bacteria,
whose energy for growth is derived from sunlight
and their source of carbon comes from carbon
dioxide or organic carbon. There are two groups of
phototrophic bacteria, i.e., anoxygenic
phototrophic bacteria and oxygenic phototrophic
bacteria.
Cyanobacteria or blue-green bacteria
oxygenic photosynthesis
Purple bacteria anoxygenic photosynthesis
Green bacteria
anoxygenic photosynthesis
Cyanobacteria’s are photosynthetic bacterias,also referred as bluegreen algae.
Have similar chlorophyll a to the plants.
Oxygenic phototrophy(unique in evolution)
Nostoc
anabaena
Carry out anoxygenic photosynthesis; no O2 evolved
Morphologically diverse group
Genera fall within the Alpha-, Beta-, or
Gammaproteobacteria
Contain bacteriochlorophylls and carotenoid pigments
Produce intracytoplasmic photosynthetic membranes
with varying morphologies
- allow the bacteria to increase pigment content
- originate from invaginations of cytoplasmicmembrane
Liquid Cultures of Phototrophic Purple Bacteria
Rhodospirillum rubrum
Rhodobacter sphaeroides
Rhodopila globiformis
Purple Sulfur
BacteriaPurple Non-sulfur
Bacteria
› Use hydrogen sulfide (H2S) as an electron
donor for CO2 reduction in photosynthesis
› Sulfide oxidized to elemental sulfur (So) that
is stored as globules either inside or outside
cells
Sulfur later disappears as it is oxidized to
sulfate (SO42-)
› The family Chromatiaceae contains the purple-sulphur bacteria
Photomicrographs of Purple Sulfur Bacteria
Chromatium okenii Thiospirillum jenense
Thiopedia rosea Ectothiorhodospira mobilis
› Many can also use other reduced sulfur
compounds, such as thiosulfate (S2O32-)
› All are Gammaproteobacteria
› Found in illuminated anoxic zones of lakes and
other aquatic habitats where H2S accumulates,
as well as sulfur springs
Blooms of Purple Sulfur Bacteria
Lamprocystisroseopersicina
Algae (Spirogyra)
Chromatiumsp.
Thiocystis sp.
› Originally thought organisms were unable to use sulfide as an
electron donor for CO2 reduction, now know most can
› Most can grow aerobically in the dark as chemoorganotrophs
› Some can also grow anaerobically in the dark using
fermentative or anaerobic respiration
› Most can grow photoheterotrophically using light as an energy
source and organic compounds as a carbon source
› All in Alpha- and Betaproteobacteria
› The family Rhodospirillaceae contains the purple non-sulphur
bacteria
Phaeospirillum fulvum Rhodoblastus acidophilus
Rhodobacter sphaeoides
Green Non-Sulphur Bacteria
Green Sulfur Bacteria
GREEN SULFUR BACTERIA
These are obligatory phototrophic bacteria
Reproduction is from binary fission mode.
Photosynthesis is achieved using bacteriophyll c,d or e.
They use H2S as electron donor for CO2 fixation.
Granules of elemental sulphur are deposited only outside the cells and the sulphur can eventually be oxidized to SO4(-2).
. In this group of bacteria flexible filaments are formed and so these are also called as the green flexi bacteria. They possess gliding mobility. Most of them do not have gas vesicles. The organisms are mainly photoorganotrophic, as the purple non-sulphur bacteria, but they can also grow as photolithotrophs as the purple non-sulphur bacteria, but they can also grow as photolithotrophs with H2S as the electron donor. In the dark they can grow aerobically as chemoheterotrophs.