Hydrogen Bacteria . 
6 3 
Hydrogen Bacteria. 
Lebedeff. “ Uber die Assimilation des Kohlenstoffes bei Wasserstoff- 
oxydierenden Bakterien.” Ber. d. d. bot. Ges. XXVII, 1909, p. 598. 
Niklewski. “ Ober die Wasserstoffoxydation durch Mikroorganismen.” 
Jahrb. f. wiss. Bot., 1910, p. 113. 
Another group of bacteria has lately been added to those 
capable of the chemosynthetic assimilation of C0 2 . They appear 
to be of general occurrence in the soil and have the remarkable 
property of being able to oxidise free hydrogen in considerable 
quantity. 
Lebedeff obtained what he considered pure cultures of such 
bacteria, and found that they could live either auto- or hetero- 
trophically. On inorganic media they obtained their carbon from 
C0 2 , and the energy necessary for its assimilation by rapid 
oxidation of hydrogen, giving out at the same time some free 
nitrogen ; when supplied with suitable organic substances less 
hydrogen was oxidised, and no nitrogen evolved. Lebedeff con¬ 
cludes that his results can be explained by supposing that the 
oxidation of hydrogen and assimilation of C0 2 are chemically 
independent, the latter having the same chemical basis as in photo¬ 
synthesis. In old cultures the ratio of hydrogen to oxygen absorbed 
was just 2 : 1 when allowance was made for the oxygen evolved in 
carbon-assimilation. 
Niklewski was unable to obtain pure cultures of the bacteria 
on purely inorganic media, and among agar cultures found two 
distinct forms capable of oxidising hydrogen. He found Lebedeff’s 
data insufficient for any comparison between his own and 
Lebedeff’s bacteria or methods of culture. He found later that, 
separately, the two species develop fairly well on inorganic media 
in an atmosphere consisting chiefly of hydrogen, with a little air 
and C0 2 . In the presence of more than 7—8% of oxygen neither 
developed alone, but if mixed together both flourished even in an 
explosive mixture of hydrogen and oxygen (33% 0 2 ). Both appear 
to be obligate aerobes, although a trace of oxygen is sufficient for 
their existence on organic media. 
In seeking for light on the mutual relations between these 
bacteria and their functions during symbiosis, Niklewski made 
cultures on various organic media in various atmospheres, with 
striking, but at present for the most part incomprehensible results. 
For instance he found that with one of the forms, Hydrogenomonas 
vitrea on glucose no hydrogen was oxidised, on mannite a con¬ 
siderable quantity was oxidised, on an acetate still more, i.e., 
the better the food the less hydrogen was oxidised ; but, in absence 
of C0 2 , cultures grown on glucose oxidised hydrogen vigorously, 
while on the mannite and acetate there was no growth what¬ 
ever. This may mean that CO„ is necessary for the oxidation 
of hydrogen, enough being provided in the case of glucose by 
oxidation, but none from mannite or acetate. However this may 
be, Niklewski, in opposition to Lebedeff, regards the oxidation of 
hydrogen by these bacteria as an indirect process involving an 
