A comparison of 16S rRNA gene (rDNA) sequences was made among type strains of 69 Bacillus species approved in the International Journal of Systematic Bacteriology (IJSB) until 1998. The results suggested that 5′ end region (approx. 275 bp) was the hypervariant region (HV region) in the gene and was highly specific for each type strain. Furthermore, a sequence analysis of the HV region of Bacillus strains revealed that this region was highly conserved within the species. These results indicate that the HV region is a useful index for the identification or grouping of Bacillus species.
Chemotaxonomic and phylogenetic characteristics of Sphingomonas strains isolated from plants of the family Gramineae were investigated. All strains contained the monosaccharide (glucuronic acid) type of glycosphingolipid (GSL-1). Most were found also to contain the oligosaccharide-type glycosphingolipids. Fatty acid and sphingosine profiles of the isolates were identical, although the ratio of the contents varies among the isolates. They all contained ubiquinone Q-10, and the G+C contents were from 66 to 68%. Phylogenetic analysis using 16S rRNA gene base sequences revealed that all the isolates were placed in the phylogenetic group of Sphingomonas paucimobilis in the α-4 subclass of Proteobacteria. By DNA-DNA hybridization experiments, the plant isolates were divided into five genotypic groups (groups 1 to 5). The strains of group 5 showed common physiological characteristics and formed pink-yellow colored colonies. Based on these results, Sphingomonas roseoflava sp. nov. was proposed for that homology group.
One of at least two chitosanases secreted in the culture filtrate of Bacillus subtilis KH1 was purified by two sequential DEAE Sepharose CL-6B chromatographies, followed by Sephacryl S-100 HR gel chromatography. The purified enzyme was homogenous as judged by SDS-PAGE. It showed an estimated molecular weight and pI of 28,000 and 8.3, respectively. The enzyme drastically reduced the viscosity of highly deacetylated chitosan substrates, with the subsequent formation of chitooligosaccharides [(GlcN)n, n=2–6]. No activity toward carboxymethylcellulose (CMC), chitobiose (GlcN)2, or chitotriose (GlcN)3 was detected. Separation and quantification of products of hydrolysis of 10% (w/v) solutions of chitooligosaccharides, (GlcN)n, n=2–6, by HPLC showed the splitting of (GlcN)n, n=4–6, in an endo-splitting manner. Oligomers comprising higher units than the starting substrate were also detected, indicating transglycosylation activity. The amino terminal sequence of this enzyme (A-G-L-N-K-D-Q-K-R-R) is identical to that of the chitosanase derived from Bacillus pumilus BN262 and to the deduced amino terminal sequences of Bacillus subtilis 168 and Bacillus amyloliquefaciens UTK chitosanases.
Increased intracellular concentrations of the initiator protein Rep (or RepA) interfere with pSC101 DNA replication, and mutated Rep proteins that result in an increase in plasmid copy numbers do not inhibit the replication. A rep mutant (repinh) defective in the inhibitory activity was isolated and found to be a new high copy number mutant. The inhibitory function of Rep was enhanced by the coexistence of directly repeated sequences (DR; iterons) in the replication origin region (ori), but not by the inverted repeat sequences (IR) in ori and the rep promoter. This synergistic effect of Rep and DR sequences for the replication inhibition was dependent on their intracellular concentrations. Considering that DR sequences are the specific binding sites of the Rep monomer form, the Rep monomer-DR complex might be responsible for the inhibition of the plasmid replication. Furthermore, the Rep monomer in the crude cell extracts facilitated dimerization of DR DNA fragments by DNA ligase. Neither synergistic inhibitory function with DR nor Rep mediated dimerization of DR DNA was observed in high copy number mutant Rep proteins. The role of the Rep-iteron complex in the copy number control of pSC101 is discussed.
Serial observations were carried out on cultures of five morphospecies of the genus Microcystis Kützing ex Lemmermann 1907, Microcystis aeruginosa (Kützing) Kützing, Microcystis ichthyoblabe Kützing, Microcystis novacekii (Komárek) Compére, Microcystis viridis (A. Brown) Lemmermann, and Microcystis wesenbergii (Komárek) Komárek in Kondratieva. Many strains maintained colony forms characteristic of their morphospecies, and others showed morphological variations, some of which were characteristic of other morphospecies. M. novacekii displayed several morphotypes including some characteristics of M. aeruginosa and M. ichthyoblabe. M. wesenbergii also showed great morphological variability and showed morphotypes characteristic of M. aeruginosa. Distinction among these morphospecies, therefore, seemed to be obscure or impossible. We conclude that the current classification of the genus Microcystis, chiefly based on morphological characteristics, is no longer valid and must be reviewed in light of our observations that one strain may have various colony forms.
A new hyphomycetous genus, Pseudosigmoidea, is established with a single species, P. cranei, based on ATCC 16660 previously identified as Sigmoidea prolifera. The conidial ontogeny of Pseudosigmoidea is enteroblastic, and its conidiogenesis is phialidic. On the other hand, Sigmoidea is redescribed with holoblastic conidial ontogeny and with conidiogenous cells proliferating sympodially.