Download Sulfate-reducing bacteria (SRB) are most notable for the

Sulfate-reducing bacteria (SRB) are most notable for the
conspicuous end product of their respiratory metabolism,
hydrogen sulfide, which is chemically reactive and quite toxic to
plants, animals and humans.
Since these bacteria are killed by exposure to atmospheric
oxygen, the environmental niches most frequently occupied by
these bacteria are anaerobic.
Thus members of the SRB are classified by only two
characteristics, their oxygen sensitivity and their ability to use
sulfate as a terminal electron acceptor. This sweeping
classification includes many types of bacteria, Gram negative
and positive, mesophilic and thermophilic, marine and
freshwater, Eubacteria and Archaea. However, members of the
genus Desulfovibrio are the most readily cultured and are the
only SRB that have been subjected to molecular biological
analysis.
Sulfate reduction is a dominant anaerobic carbon oxidation
pathway along the margins accounting for the oxidation of 50%
of the total organic carbon in some systems
More recent studies (Lovley et al., 1993) have documented the ability
of a number of Desulfovibrio strains to reduce toxic metals such as
uranium and chromium, a process that results in the production of less
water-soluble species.
The distinguishing characteristics of Desulfovibrio species
are that they contain desulfoviridin. Desulfovibrio oxidize
their energy source to that of acetate and excrete this as
their end product.
Desulfovibrio also uses hydrogen, lactate, and pyruvate as
electron donrs.
This genus can grow easily on a sulfate-lactate medium in
the absence of oxygen. There are a number of species
fwithin the genus Desulfovibrio.
The economic and environmental processes which have historically
driven the desire to understand the metabolism of the SRB include
underground corrosion of iron or steel gas or water pipes and
generation of noxious sulfide during digestion of domestic and
agricultural wastes.
These bacteria have been a particular problem for the petroleum
industry not only because of their role in metal corrosion but also
because of the souring of the petroleum by the hydrogen sulfide
generated and the health hazard presented by this gas. In particular,
the possibility that these bacteria utilize a novel hydrogen cycling
mechanism to generate or augment the proton gradient across the
cytoplasmic membrane (Odom and Peck, 1981) has stimulated much
discussion.
Obligate anaerobes. Curved rod-shaped cells.
0.5-1.5 x 2.5-10 um; Non-spore forming.
Gram negative; Polarly flagellated.
Contains desulfoviridin; It is a sulfate-Reducing Proteobacteria.
Desulfovibrio desulfuricans
List of Species
List of Species
Desulfovibrio acrylicus
Desulfovibrio aespoeensis
Desulfovibrio aestuarii
Desulfovibrio africanus
Desulfovibrio alaskensis
Desulfovibrio alcoholivorans
Desulfovibrio aminophilus
Desulfovibrio baarsii
Desulfovibrio baculatus
Desulfovibrio bastinii
Desulfovibrio burkinensis
Desulfovibrio capillatus
Desulfovibrio carbinolicus
Desulfovibrio cuneatus
Desulfovibrio desulfuricans
Desulfovibrio desulfuricans subsp. desulfuricans
Desulfovibrio desulfuricans subsp. termitides
Desulfovibrio ferrophilus
Desulfovibrio fluorescens
Desulfovibrio fructosivorans
Desulfovibrio gabonensis
Desulfovibrio giganteus
Desulfovibrio giganteus subsp. termitides
Desulfovibrio gigas
Desulfovibrio gracilis
Desulfovibrio halophilus
Desulfovibrio hydrothermalis
Desulfovibrio indonesiensis
Desulfovibrio inopinatus
Desulfovibrio intestinalis
Desulfovibrio litoralis
Desulfovibrio longus
Desulfovibrio magneticus
Desulfovibrio mexicanus
Desulfovibrio orientis
Desulfovibrio oxyclinae
Desulfovibrio piger
Desulfovibrio profundus
Desulfovibrio salexigens
Desulfovibrio sapovorans
Desulfovibrio senezii
Desulfovibrio simplex
Desulfovibrio sp.
Desulfovibrio sulfodismutans
Desulfovibrio termitidis
Desulfovibrio thermophilus
Desulfovibrio vietnamensis
Desulfovibrio vulgaris subsp. oxamicus
Desulfovibrio vulgaris subsp. vulgaris
Desulfovibrio zosterae
Members of the genus Desulfovibrio commonly reside in the soil and aquatic
habitats. Since these organisms are strict anaerobes, both aquatic and terrestrial
environments are made anoxic as a result of microbial decomposition.
The surrounding elements in such an environment are rich in organic material and
in sulfate.
Isolation of Desulfovibrio is facilitated by using the anoxic lactate-sulfate medium
with ferrous iron incorporated into the culture. As the sulfate is reduced to sulfite,
the sulfite interact with the ferrous iron to generate a black medium (see Figure B to
the left). This new medium is chemically called ferrous sulfide and it is insoluble.
The blackening of the culture indicates that sulfate reduction is taking place and that
the iron is acting as a detoxifier for the harmful sulfide; thus, enabling a higher
growth yield for the sulfate-reducing bacteria to grow. To further isolate the sulfatereducing bacteria, streaking can be used both on a Petri plate or in roll tubes. The
shaken tube method involves placing a small amount of liquid with the bacteria in
the agar growth medium and diluted. Once the medium is solidified, black colonies
of the bacteria will appear and can be cultivated into a pure culture. Due to how
common Desulfovibrio is found in both aquatic and terrestrial habitats, this genus is
the most studied of the sulfate-reducing proteobacteria.
Desulfovibrio vulgaris is a model for the study of the energy metabolism of
sulfate-reducing bacteria. Sulfate-reducing bacteria have an important
economic impact because they are involved in biocorrosion of ferrous metals in
anaerobic environment. For example, their metabolism has several negative
consequences for the petroleum industry (e.g. corrosion of the pumping
machinery). These bacteria also contribute to bioremediation of toxic metal
ions.