Xanthomonas campestris pv. glycines strain AM2 (XcgAM2), the etiological agent of bacterial pustule disease of soybean, exhibited post-exponential rapid cell death (RCD) in LB medium. X. campestris pv. malvacearum NCIM 2310 and X. campestris NCIM 2961 also displayed RCD, though less pronouncedly than XcgAM2. RCD was not observed in Pseudomonas syringae pv. glycinea, or Escherichia coli DH5α. Incubation of the post-exponential LB-grown XcgAM2 cultures at 4°C arrested the RCD. RCD was also inhibited by the addition of starch during the exponential phase of LB-growing XcgAM2. Protease negative mutants of XcgAM2 were found to be devoid of RCD behavior observed in the wild type XcgAM2. While undergoing RCD, the organism was found to transform to spherical membrane bodies. The presence of membrane bodies was confirmed by using a membrane specific fluorescent label, 1,6-diphenyl 1,3,5-hexatriene (DPH), and also by visualizing these structures under microscope. The membrane bodies of XcgAM2 were found to contain DNA, which was devoid of the indigenous plasmids of the organism. The membrane bodies were found to bind annexin V indicative of the externalization of membrane phosphatidyl serine. Nicking of DNA in XcgAM2 cultures undergoing RCD in LB medium was also detected using a TUNEL assay. The RCD in XcgAM2 appeared to have features similar to the programmed cell death in eukaryotes.
Fifty axenic strains of planktonic Anabaena, including 24 strains of the straight form and 26 strains of the coiled form, were examined for their DNA base composition (GC content). The taxonomic value of their GC content at species level was evaluated by comparing their morphological, physiological and biochemical properties. The DNA base composition determined for all fifty strains ranged from 35.9 to 56.4 mol% GC. The straight-form strains were in the range of 35.9–56.4 mol% GC, while coiled forms were in the range of 38.1–50.3 mol% GC. In general, strains assigned to the same species showed similar DNA base composition. However, of three strains of A. affinis Lemmermann that were separated into two categories, two had 40.6–40.9 mol% GC, and the third strain 45.6 mol% GC. It is noteworthy that the DNA base composition of the newly established species A. eucompacta Li et Watanabe was 45.5 mol% GC, which differed from 39.5 mol% GC of the morphologically close species, A. compacta (Nygarrd) Hickel.
An in vitro study was conducted to examine the effects of fructooligosaccharide (FOS) at levels of 0.5, 1.0, and 1.5% on conversion of L-tryptophan to skatole and indole by a mixed bacterial population from the large intestines of pigs. Microbial suspensions were anaerobically incubated at 38°C for 24 h. Samples were periodically removed for determination of pH and indole compounds. After 24 h incubation, microbial populations in each culture media were analyzed. Addition of 0.5, 1.0, and 1.5% FOS to the slurries with L-tryptophan significantly decreased the skatole concentration, the peak value of indole-3-acetic acid and the medium pH. The viable counts of Bifidobacterium were significantly higher as compared with the control. Addition of 1.0 and 1.5% FOS significantly decreased the rate of tryptophan degradation and the relative rate of skatole production. The relative rate of indole production was significantly increased. The viable counts of Clostridium and Escherichia coli were significantly reduced. The total viable counts of anaerobes were significantly increased. These results suggest that the reduced concentration of skatole observed in the presence of FOS may be caused by the decreased tryptophan degradation due to the increased need for amino acids in the synthesis of bacterial cellular protein, and by shifting microbial metabolism of tryptophan toward indole production at the expense of skatole, which might result from the changed microbial ecosystem and pH. Our observations open the possibility of inhibiting microbial production of skatole and decreasing the skatole concentration in backfat by feeding pigs diets containing FOS, but it remains to be demonstrated in vivo.
The effect of sodium acetate was studied on the change of the growth yield, the production of L- and D-lactic acid, and the activity of lactate dehydrogenases (LDHs; L-lactate dehydrogenase [EC 188.8.131.52, L-LDH] plus D-lactate dehydrogenase [EC 184.108.40.206, D-LDH]), fructose-1, 6-bisphosphate aldolase [EC 220.127.116.11, FBP-aldolase], and phosphofructokinase [EC 18.104.22.168, PFK] of Lactobacillus sakei NRIC 1071T and Lactobacillus plantarum NRIC 1067T. The growth yield of L. sakei NRIC 1071T was increased 1.6 times in the presence of sodium acetate compared with its absence. The activity of LDHs in L. sakei NRIC 1071T and L. plantarum NRIC 1067T was retained longer under the addition of sodium acetate in the reaction mixture. As a result, these strains produced much more lactic acid in the presence of sodium acetate compared with its absence. Furthermore, the activity of L-LDH in L. sakei NRIC 1071T cultivated in the presence of sodium acetate increased three times or more compared with the activity of the cells cultivated in its absence. Consequently, the type of stereoisomers of lactic acid produced by L. sakei shifted from the DL-type to the L-type because the ratio of L-lactic acid to D-lactic acid produced became larger with the addition of sodium acetate to culture media. This phenomenon was not observed in L. plantarum NRIC 1067T. Further, the participation of lactate racemase is discussed from the viewpoint of the production of D-lactic acid by L. sakei.
The long surface antigen (L-HBsAg) of hepatitis B virus (HBV) plays a central role in the production of infectious virions. During HBV morphogenesis, both the PreS and S domains of L-HBsAg form docking sites for the viral nucleocapsids. Thus, a compound that disrupts the interaction between the L-HBsAg and nucleocapsids could serve as a therapeutic agent against the virus based upon inhibition of morphogenesis. Synthetic peptides correspond to the binding sites in L-HBsAg inhibited the association of L-HBsAg with core antigen (HBcAg). A synthetic peptide carrying the epitope for a monoclonal antibody to the PreS1 domain competed weakly with L-HBsAg for HBcAg, but peptides corresponding to a linear sequence at the tip of the nucleocapsid spike did not, showing that the competing peptide does not resemble the tip of the spike.
Phenotypic and phylogenetic studies were performed on two myxobacterial strains, SMP-2 and SMP-10, isolated from coastal regions. The two strains are morphologically similar, in that both produce yellow fruiting bodies, comprising several sessile sporangioles in dense packs. They are differentiated from known terrestrial myxobacteria on the basis of salt requirements (2–3% NaCl) and the presence of anteiso-branched fatty acids. Comparative 16S rRNA gene sequencing studies revealed that SMP-2 and SMP-10 are genetically related, and constitute a new cluster within the myxobacteria group, together with the Polyangium vitellinum Pl vt1 strain as the closest neighbor. The sequence similarity between the two strains is 95.6%. Based on phenotypic and phylogenetic evidence, it is proposed that these two strains be assigned to a new genus, Haliangium gen. nov., with SMP-2 designated as Haliangium ochraceum sp. nov. (=JCM 11303T=DSM 14365T), and SMP-10 as Haliangium tepidum sp. nov. (=JCM 11304T=DSM 14436T).