Chemoautotrophs and photosynthetic eubacteria

3. troph =
nourishment
auto = self
chemo =
chemical
chemoutotrophs

4.  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 .

5.  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

6.  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

7. Chemolithotrophy: Energy from the
Oxidation of Inorganic Electron Donors

8.  Carry out respiration by coupling the
oxidation of an inorganic compound
to the reduction of membrane-bound
electron carriers:
e–  electron transport chain
 proton motive force
 ATP synthesis
8
inorganic electron donor
 protons pumped out
most ATP produced by oxidative
phosphorylation

9.  sulfur oxidizers
 nitrifying bacteria
 iron oxidizers
Hydrogen oxidizers.
 Anammox Bacteria

10. ATP has a free energy of -31.8
kJ/mol

12.  2H2 + 02
 2H20 (1)
 2 H2 + C02
 <CH20 > + H20 (2)
 6H2 + 202 + CO2
 <CH20> +5 H20 (3)

13. Hydrogen Bacteria
Ralstonia eutropha is a gram-negative soil bacterium of the
betaproteobacteria class

15.  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.

16.  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.

17.  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 (NO-) to nitrate by nitrite-oxidizing
2
bacteria (NOB), represented by Nitrobacter species.

18.  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)

19. 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.

20.  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.

21. The ammonia-oxidizing bacteria produce nitrite which is
then oxidized by the nitrite-oxidizing bacteria to nitrate.

22. Nitrosococcus
NH
3
NO2
–
Nitrobacter
NO2
– 
NO3
–
No single bacterium oxidizes ammonia
all the way to nitrate.

23.  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

28. “White Streamers”
color due to sulfur granules in cells

30. 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

31. The iron bacteria are chemolithotrophs that use ferrous iron (Fe2+) as
their sole energy source.

32. Most iron bacteria grow only at acid
pH and are often associated with
acid pollution from mineral and coal
mining.

33. 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

36. Anammox - Anaerobic ammonium
36
NH4
+ + NO2
oxidation
-  N2 + 2 H2O

37. Brocadia anammoxidans
Anammox bacteria:
Planctomyces group
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.

38.  Enrichment culture of the anammox
bacterium Kuenenia stuttgartiensis

40. Eubacteria, known as "true bacteria," are prokaryotic
(lacking nucleus) cells that are very common in
human daily life.

41.  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.

42.  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.

46. Cyanobacteria or blue-green
bacteria
 oxygenic photosynthesis
Purple bacteria
 anoxygenic photosynthesis
Green bacteria
anoxygenic photosynthesis

47.  Cyanobacteria’s are photosynthetic
bacterias,also referred as bluegreen algae.
 Have similar chlorophyll a to the plants.
 Oxygenic phototrophy(unique in evolution)

51. Nostoc

52. anabaena

53. 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 cytoplasmic
membrane

54. Liquid Cultures of Phototrophic Purple Bacteria
Rhodospirillum
rubrum
Rhodobacter
sphaeroides
Rhodopila
globiformis

56. Purple Sulfur
Bacteria
Purple Non-sulfur
Bacteria

57. › 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 (SO2-)
4
› The family Chromatiaceae contains the purple-sulphur
bacteria

58. Photomicrographs of Purple Sulfur Bacteria
Chromatium okenii Thiospirillum jenense
Thiopedia rosea Ectothiorhodospira
mobilis

59. › Many can also use other reduced sulfur
compounds, such as thiosulfate (S2O3
2-)
› All are Gammaproteobacteria
› Found in illuminated anoxic zones of lakes and
other aquatic habitats where H2S accumulates,
as well as sulfur springs

60. Blooms of Purple Sulfur Bacteria
Lamprocystis
roseopersicina
Algae (Spirogyra)
Thiocystis sp.
Chromatium
sp.

61. › 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

62. Phaeospirillum fulvum Rhodoblastus
acidophilus
Rhodobacter
sphaeoides

64. Green Non-
Sulphur Bacteria
Green Sulfur
Bacteria

65. 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).

68.  . 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.