8. REACTIONS OF INORGANIC SURSTANCES
373
denitrificans as for the other members of the genus, the sole source of
assimilable nitrogen is ammonia, which is usually provided in the culture medium as ammonium chloride.
Among the species listed in Table VIII, three are distinguished by
the fact that they can make use of other sources of energy than inorganic sulfur compounds. T. novellus is a facultative autotroph which
can grow on organic media. T. ferrooxidans can use the oxidation of
Fe
2+ to Fe
3+ as an energy source. Finally, T. thiocyanooxidans can use
thiocyanate as the sole source of energy and of carbon and nitrogen.
The metabolic systems characteristic of the latter two organisms are
described in Sections V,A and V,B.
Several species of thiobacilli of doubtful validity have been reported.
Parker (88) described a bacterium responsible for the corrosion of
concrete in sewers, with the production of large quantities of free sulfuric acid from the sulfides present in sewage. This organism, which he
called T. concretivorus, does not seem to differ morphologically or biochemically from T. thiooxidans.
Baalsrud (89) and Vishniac and Santer (38) recently reviewed the
extensive literature on the thiobacilli, their taxonomy, methods of culture, and physiological properties.
2. Beggiatoaceae and Achromaciaceae
These two families of bacteria comprise nonphotosynthetic sulfooxidizing organisms which differ from the thiobacilli because they contain endocellular granules of elementary sulfur.
The family of Beggiatoaceae, to which "Bergey's Manual" (61) assigns 4 genera (Beggiatoa, Thioploca, Thiothrix, and Thiospirillopsis),
is characterized by filamentous, unbranched, multicellular, alga-like
cells. These organisms resemble the algae OsciUatoria; they share their
very particular means of motion by reptation, but differ in lacking
chlorophyll and phycocyanin. The family of Achromaciaceae, which
consists of three genera (Achromatium, Thiovulum, and Macromonas),
is made up of unicellular, nonfilamentous, mobile or immobile, nonpigmented organisms, some of which closely resemble the Myxophyceae.
The classification of these bacteria and their place in taxonomy are
not yet established clearly and are the subject of controversies discussed
by Bisset and Grace (62). Little is known about their metabolism although they were first studied in 1887. Winogradsky (90) showed that
the oxidation of sulfide by Beggiatoa alba proceeds in two steps. The
first is the aerobic oxidation to elementary sulfur which accumulates in
the cell as strongly refringent granulations:
H 2 S + 0.5 0 2 = S° + H 2 0 + 41 kcal.
373
denitrificans as for the other members of the genus, the sole source of
assimilable nitrogen is ammonia, which is usually provided in the culture medium as ammonium chloride.
Among the species listed in Table VIII, three are distinguished by
the fact that they can make use of other sources of energy than inorganic sulfur compounds. T. novellus is a facultative autotroph which
can grow on organic media. T. ferrooxidans can use the oxidation of
Fe
2+ to Fe
3+ as an energy source. Finally, T. thiocyanooxidans can use
thiocyanate as the sole source of energy and of carbon and nitrogen.
The metabolic systems characteristic of the latter two organisms are
described in Sections V,A and V,B.
Several species of thiobacilli of doubtful validity have been reported.
Parker (88) described a bacterium responsible for the corrosion of
concrete in sewers, with the production of large quantities of free sulfuric acid from the sulfides present in sewage. This organism, which he
called T. concretivorus, does not seem to differ morphologically or biochemically from T. thiooxidans.
Baalsrud (89) and Vishniac and Santer (38) recently reviewed the
extensive literature on the thiobacilli, their taxonomy, methods of culture, and physiological properties.
2. Beggiatoaceae and Achromaciaceae
These two families of bacteria comprise nonphotosynthetic sulfooxidizing organisms which differ from the thiobacilli because they contain endocellular granules of elementary sulfur.
The family of Beggiatoaceae, to which "Bergey's Manual" (61) assigns 4 genera (Beggiatoa, Thioploca, Thiothrix, and Thiospirillopsis),
is characterized by filamentous, unbranched, multicellular, alga-like
cells. These organisms resemble the algae OsciUatoria; they share their
very particular means of motion by reptation, but differ in lacking
chlorophyll and phycocyanin. The family of Achromaciaceae, which
consists of three genera (Achromatium, Thiovulum, and Macromonas),
is made up of unicellular, nonfilamentous, mobile or immobile, nonpigmented organisms, some of which closely resemble the Myxophyceae.
The classification of these bacteria and their place in taxonomy are
not yet established clearly and are the subject of controversies discussed
by Bisset and Grace (62). Little is known about their metabolism although they were first studied in 1887. Winogradsky (90) showed that
the oxidation of sulfide by Beggiatoa alba proceeds in two steps. The
first is the aerobic oxidation to elementary sulfur which accumulates in
the cell as strongly refringent granulations:
H 2 S + 0.5 0 2 = S° + H 2 0 + 41 kcal.