370 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Formation of Sulphuretted Hydrogen in Town Drains, and Genus 

 Aerobacter g. n.* — The attention of Prof. W. Beijerinck was originally 

 directed to the formation of sulphuretted hydrogen in town drains by 

 the discovery of an essentially anaerobic non-sporing spirillum which, 

 owing to its sulphate reducing-properties, was designated Spirillum de- 

 sidfuricans. As the result of further research in this direction, he 

 now suggests that the presence of H 2 S in drains arises not only from 

 the reduction of sulphates, but also from free sulphur and from albu- 

 minous bodies. This decomposition of albuminous bodies must be 

 brought about either by aerobic organisms or by microbes which are 

 potential, or, to express the idea more fitly, temporary anaerobes. 



These organisms were found by a special method of investigation 

 (see p. 391) to form sulphide, and were thus easily detected in the 

 lead-medium used for their cultivation. The outcome of the present 

 research is the suggestion that these gas-forming species endowed with 

 this temporary anaerobism should be classed together in the genus 

 Aerobacter, a detailed account of the general characters of which is 

 given. A special description of the more prominent species is also 

 supplied ; but as these are known under other names, it will suffice to 

 mention their designations : — (1) Aerobacter aerogenes = Bacillus lactis 

 aerogenes; (2) Aerobacter viscosum ; (3) Aerobacter coli = B. coli com- 

 munis ; (4) Aerobacter coli var. infusionum ; (5) Aerobacter lique- 

 faciens. 



The author concludes by discussing the different sources from which 

 Aerobacter derives its sulphur ; these sources are albumen, sulphur 

 itself, sulphites, and sulphates. 



Fat-reserves of Bacteria.f— Prof. A. Meyer identifies the granules 

 and droplets seen in bacteria as fat-globules, partly by specific staining 

 and partly by chemical reactions. The stains used were methylen-blue, 

 Sudan ill. , and a yellow stain (dimethylamidoazobenzol), the fat being 

 coloured red or yellow. The chemical reaction was obtained by first 

 breaking up a bacterial mass with quartz sand, extracting with ether, and 

 treating with petroleum benzin. After evaporation the residue was found 

 to leave a greasy mark on paper, and to become saponified on treatment 

 with alcohol and caustic potash. On the addition of" sulphuric acid fatty 

 acids separated out. The glycerin test applied to the filtrate failed. 

 The fat is to be regarded as reserve-substance, which is accumulated 

 when the conditions of nutrition are favourable, and is used up in spore- 

 formation. The foregoing remarks apply chiefly to B. tumescens, but 

 the substance containing a fatty acid found in tubercle bacilli is alluded 

 to. Beyond the fact of its existence little is known of it ; its location 

 is not yet settled, and what part it plays in the biology of the plant is 

 dubious. 



Iodine - Staining Polysaccharides of Bacteria.J — Prof. A. Meyer 

 gives reasons for believing that there are two carbohydrates which stain 

 with iodine, and which are stored up by bacteria as reserve-substances. 

 One is red staining, the other blue staining. These reserve-substances 

 are colourless, highly refractive, -diffuse with difficulty, cannot be ex- 



* Centralbl. Bakt. u. Par., 2" Abt., ri. (1900) pp. 193-206. 



+ Flora, lxxxvi. (1899) pp. 431-9 (1 pi.).. J Tom. cit., pp. 440-9. 



