The cellular fatty acid composition of 27 strains of gram-negative obligately anaerobic rods was determined by gas-liquid chromatography. Results showed that a variety of acids was detected in these organisms, and comparison of the relative amount of each of the acids was useful in distinguishing several species. A dendrogram based on their fatty acid composition was made, and this analysis appeared to be an aid in the grouping of the bacteria.

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Examination of non-methanogenic anaerobic bacteria in sewage digestor fluid was attempted by the anaerobic roll tube method. For the enumeration of anaerobic bacteria in digestor fluid, rumen fluid-glucosecellobiose-agar (RGCA) gave as good results as previously reported in the rumen and other ecosystems like intestines and feces, under the 100% CO2 gas phase. However, under the mixed gas phase (95 % N2 and 5 % C02), higher colony counts were obtained with YLS agar, which contained the supernatant of autoclaved sewage digestor fluid, than with RGCA. Colony counts of anaerobic bacteria decreased with the progress of fermentation of waste and the proportion of facultative anaerobes in the isolated anaerobes also decreased. Large variations in the distribution pattern of bacteria were usually observed between the results obtained from three digestors investigated. However, Streptococcus and Gram-negative curved rods were commonly isolated from the three digestors as predominant groups.The anaerobic roll tube method devised by HUNGATE (1) facilitated isolation and cultivation of strictly anaerobic bacteria, and a significant progress has been made in the studies of microbial ecosystem in the rumen (2). This method was also applied to isolate anaerobic bacteria from intestines (3, 4) and feces (5, 6).However, application of this method to the enumeration and isolation of anaerobic bacteria in other ecosystems, such as the soil and sewage digestors has been very scarce. Our knowledge about anaerobic bacteria in these ecosystems is restricted to only a few kinds of bacteria and increase in the information about other anaerobic bacteria in these ecosystems is being expected.The anaerobic ecosystem of sewage digestor resembles that of rumen. The process of fermentation in digestors involves two stages, non-methanogenic and methanogenic. At the non-methanogenic stage, organic matters poured into digestors are decomposed to lower fatty acids and other low-molecular compounds. 317

The occurrence of free ceramides at high concentrations was demonstrated in the chloroform-methanol extractable lipids of Bacteroides fragilis NCTC 9343. The long-chain bases were isolated from the free ceramides and identified as branched and normal saturated dihydroxy bases with carbon chains consisting of 17, 18, and 19 atoms. The major fatty acid was 3-hydroxy 15-methylhexadecanoic acid. The major molecular species of the ceramides were identified by gas chromatography-mass spectrometry and gas chromatography of the cleaved products as LCB-d-iso17: 0-3-OH iso17: 0 FA, LCB-d-anteiso17: 0-3-OH iso17: 0 FA, LCB-d-iso18: 0-3-OH iso17: 0 FA, and LCB-d-anteiso19: 0-3-OH iso17: 0 FA.

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