- Volume 66, Issue 3, 1971

SUMMARY: The walls of two rod mutants of Bacillus subtilis 168 trp and of the parent grown under the same conditions were identical in qualitative composition, with the possible exception of rod-5 grown on minimal medium without added sodium chloride; these walls did not contain galactosamine. The amounts of α, e-diamino-pimelic acid and glutamic acid in the walls of the mutants were lowered by growth on minimal media supplemented by o·8 m-sodium chloride, whereas in the parent these growth conditions led to increases in the contents of these two amino acids. The mucopeptide of mutant rod-4 was very little cross-linked when growing under conditions that lead to a round form, but this also applied to the mucopeptide of the parent grown under the same conditions. When the mutant grew as a rod, its mucopeptide again had the same degree of cross-linking as that of the parent grown in rich media. The concentration of organic phosphorus in the walls of the mutants, presumed to be present as teichoic acid, was about the same as that in the parent and was unaffected by the growth conditions. Thus the chemistry of the walls of rod mutants did not provide obvious evidence of expression of the genetic lesion.

SUMMARY: Germ-tube emergence in Aspergillus nidulans exhibits partial synchrony. Germ tubes were first detected at 210 min. after inoculation of spores into a liquid medium. Almost all spores produced germ tubes within 360 min., 49.5 % of them doing so between 240 and 300 min. Increase in dry weight was first detected at 120 min. and various constituents at the following times: RNA (30 min.), Kjeldahl nitrogen (30 min.), protein (150 min.) and DNA (180 min.). Pauses in the increase of DNA, RNA and protein were observed. The DNA content per nucleus during the first replication cycle reached twice that of the resting spore, but at later stages of germination values only 10 % higher were observed. Spores containing 2, 4 and 8 nuclei were first detected at 270, 390 and 480 min. respectively.

SUMMARY: The utilization and translocation of 14C by micro-organisms, especially fungi, was shown to occur during the decomposition of labelled plant residues in agar cultures and in soil. Utilization was demonstrated by the evolution of 14CO2 and by autoradiograms that showed 14C within micro-organisms. Translocation was indicated by labelled structures occurring on coverslips at a distance from the substrate, and by the labelling of sclerotia which had accumulated 14C preferentially nearly 1 cm. from the plant residues. Rhizoctonia solani, Trichoderma sp. and Streptomyces flavovirens, shown to be cellulolytic on cotton cellulose agar, were similarly active in agar and soil cultures containing radioactive plant residues. Labelled structures of Fusarium spp., Rhizoctonia spp., Humicolagrisea, Xylaria spp. and fungi with non-sporing dark mycelia were detected in non-sterile soil during the later stages of the decomposition of the labelled plant residues when a marked fall in carbon content was occurring. The autoradiographic technique employed here enables organisms that probably act as primary agents in the degradation of plant residues to be distinguished from those that do not.

SUMMARY: A numerical classification study was carried out on 177 strains of Klebsiella and related groups. Three methods of numerical classification were used: median sorting, single linkage cluster analysis and minimum spanning tree. All three contributed to the final decision on the taxa, but yielded substantially the same results. Of the three, the median sorting, if used alone, would have provided the most information.

The validity of the genus Klebsiella was confirmed but the inclusion of the three recognized species of Enterobacter in one genus was not confirmed. The genus Klebsiella was divided into six taxa, one of which is proposed as K. mobilis synon. Enterobacter aerogenes. E. cloacae occupied a rank similar to that of the genus Klebsiella, while E. liquefaciens was most closely related to the genus Serratia and it is proposed to include it as S. liquefaciens. Enterobacter ‘pigmentés’ was found to be closely related to Chromobacterium typhiflavum.

SUMMARY: Of the 49 strains of Trichosporon yeasts studied, 40 were retained in the genus and assigned to 10 species. The others were transferred to the genera Candida and Endomycopsis. The DNA base composition was determined for a representative of each Trichosporon species. On the basis of guanine and cytosine content (% GC), the species were arranged into four groups: (a) about 55 % GC, Trichosporon aculeatum, T. aquatile, T. cutaneum, T. inkin and T. pullulans; (b) about 64 % GC, T. eriense, T. fermentans and T. infestans; (c) 59 % GC, T. capitatum and (d) 45 % GC, T. penicillatum.

For 25 strains of the genus, 81 characteristics were selected for inclusion in a numerical taxonomic analysis with the aid of a computer. The dendrogram of the similarity values arranged these strains into three major branches arising at the 66 % S level. Branch I includes Trichosporon aculeatum, T. cutaneum, T. infestans, T. inkin and T. pullulans. Branch II is limited to T. aquatile. Branch III includes T. capitatum, T. eriense, T. fermentans and T. penicillatum. Species arising from branch I at differing S levels are T. aculeatum at 68 % S, T. pullulans at 72 % S, T. inkin at 75 % S and T. infestans at 78 % S. The remaining strains in branch I belong to the T. cutaneum group.