Iron-Bacteria. 
107 
accumulation of iron do not depend upon the activity of the 
organism and are not essential to it: a similar accumulation was 
shewn to take place by adsorption and chemical oxidation in the 
sheaths of dead cells. He supposed that Leptothrix is merely 
heterotrophic and that in Winogradsky’s cultures the minute traces 
of organic impurities were sufficient for its needs. 
This seems extremely improbable as an explanation of 
Winogradsky’s results, and it has been suggested (see Czapek, 
Biochemie 11., p. 413) that Winogradsky and Molisch were working 
with two distinct forms. Recent work by Rudolf Lieske, however, 
provides an alternative explanation, since it confirms or affords 
parallel observations to the main results of both. 
Lieske worked more especially with Spirophylhun ferrugineum, 
which forms flattened twisted filaments without any gelatinous 
sheath, and accumulates iron uniformly in the interior of the cell. 
He was quite unsuccessful in his attempts to cultivate this organism 
in organic nutrient media, or by any of the methods previously used 
for other forms. His later experiments showed that sugar, asparagin, 
and peptone, substances which provide excellent bases for the 
nutrition of most bacteria, inhibit the growth of Spirophylhun even 
in very small concentrations. By the careful exclusion of all organic 
impurities he was able to prove that it can flourish in the entire 
absence of organic nutrient substances, so long as it is supplied with 
ferrous carbonate. 
He arrived at a suitable method of culture by closely imitating 
the conditions under which he found Spirophylhun growing in nature. 
The culture fluid contained the necessary mineral salts, iron was 
supplied in the form of coarse filings, and the open vessel was 
enclosed beneath a bell-glass with air enriched with about 1% of 
C0 2 . Under these conditions sufficient iron was dissolved by the 
CO 2 in the water to enable the organism to develop luxuriantly. 
(According to Lieske’s observations water always contains a high 
percentage of C0 2 where iron-bacteria flourish.) 
Light proved to be without effect on Spirophylhun. Outside 
the laboratory it flourishes equally well in closed water-pipes and 
in iron springs. Oxidation of iron is therefore the only apparent 
source of its vital energy. Other iron salts than ferrous carbonate, 
and salts of manganese and other metals were tried without 
success; only ferrous carbonate itself, or iron or ferrous sulphide 
in presence of C0 2 (is. an indirect supply of ferrous cabonate) gave 
in Liekske’s experience any development of Spirophylhun. 
These results are obviously inconsistent with the view that the 
precipitation of iron is here purely a physico-chemical phenomenon. 
Subsequent experiments with gelatine, hardened in formaline, and 
the observation of dead filaments, showed that far more iron is 
accumulated by the living Spirophylhun than by dead adsorptive 
substances. The iron reaction is never so intense in the latter and 
they adsorb all compounds alike. Moreover the precipitation of 
ferric hydrate is an equilibrium phenomenon, the reverse reaction 
taking place in presence of an excess of C0 2 : nevertheless, Spiro¬ 
phylhun continues to accumulate iron even under these conditions. 
For Spirophylhun , then, it seems to be definitely proved that 
the accumulation of iron in large quantities is bound up with the 
