The cyanobacterium Nostoc commune is adapted to the terrestrial environment and forms a visible colony in which the cells are embedded in extracellular polysaccharides (EPSs), which play a crucial role in the extreme desiccation tolerance of this organism. When natural colonies were immersed in water, degradation of the colonies occurred within 2 days and N. commune cells were released into the water. The activities that hydrolyze glycoside bonds in various N. commune fractions were examined using artificial nitrophenyl-linked sugars as substrates. A β-D-glucosidase purified from the water-soluble fraction was resistant to 20 min of boiling. The β-D-glucosidase, with a molecular mass of 20 kDa, was identified as a cyanobacterial fasciclin protein based on its N-terminal amino-acid sequence. The 36-kDa major protein in the water-soluble fraction was purified, and the N-terminal amino-acid sequence of the protein was found to be identical to that of the water-stress protein (WspA) of N. commune. This WspA protein also showed heat-resistant β-D-galactosidase activity. The fasciclin protein and WspA in the extracellular matrix may play a role in the hydrolysis of the EPSs surrounding the cells, possibly as an aid in the dispersal of cells, thus expanding the colonies of this cyanobacterium.
An actinobacterial strain KHIAT, isolated from lichen in Tokyo, was taxonomically characterized using a polyphasic approach. The isolate is a Gram-positive, anaerobic, non-motile and rodshaped bacterium. Phylogenetic analyses based on 16S rRNA gene sequences revealed that the isolate is represented as an independent lineage distinctive from the Microbacteriaceae genera. The G + C content of DNA was 58.7 mol%. The chemotaxonomic characteristics of the isolate are cell wall peptidoglycan type (2,4-diaminobutyric acid), major cellular fatty acids (anteiso-C15:0 and iso-C16:0) and quinone type (MK-11 and MK-10). On the basis of the phenotypic and phylogenetic distinctness, it is proposed that strain KHIAT represents a novel species in a new genus of the family Microbacteriaceae, Schumannella luteola gen. nov., sp. nov. The type strain is KHIAT (=JCM 23215T=TISTR 1824T).
Three yeast strains, ST-633, ST-634 and ST-635, isolated from the fruit body of a mushroom, Coprinus sp., and rotted fruit of guava collected in the western region of Thailand, were found to represent a hitherto undescribed species. This yeast is related to Pichia nakazawae var. akitaensis, P. nakazawae var. nakazawae and Pichia philogaea in the D1/D2 domain of 26S rDNA but 12 (2.3%), 13 (2.5%) and 15 (2.8%) nucleotides are different from these taxa, respectively, suggesting the distinctness of the Thai strains at species level. Since ascospore formation was not detected, it is described as a new species of Candida, Candida kanchanaburiensis. This species is distinguished from P. nakazawae by the ability to assimilate 2-ketogluconic acid and L-lysine, and inability to assimilate soluble starch.
Lactobacillus paracasei KW3110 is a strain which has been reported to possess a strong antiallergic activity. Since many lactic acid bacteria have shown to be useful as the probiotics, the possibility of this strain for use as a probiotic was studied. An in vitro test showed that this strain is strong enough to survive in the gastric juice. In addition, this strain showed exceptionally strong adherence to human intestinal epithelial cells, Caco-2 and HT29 compared to normal L. paracasei strains. Human oral administration testing of L. paracasei KW3110 showed that this strain survived in the human gut and increased the number of bifidobacteria and lactobacilli in the fecal samples of the subjects. In addition, KW 3110 was detected in 50% of the subjects up to 1 week after the end of the administration test. These results showed that L. paracasei KW3110 has a strong ability to survive in and colonize the human gut and improve the human intestinal microflora.
We assessed the relationship between growth profile and the extent of biodegradation of Escravos light crude oil by axenic and mixed bacteria cultures in a shake flask. Eleven petroleum-degrading bacteria were isolated by enrichment from oil-contaminated soils including, Pseudomonas effusa, Pseudomonas fluorescens, Pseudomonas cruciviae, Arthrobacter tumescens, Pseudomonas species, Pseudomonas tralucida, Alcaligenes metacaligenes, Micrococcus colpogenes, Bacillus badius, Nocardia paraffinae and Bacillus species. Specific growth rates of axenic cultures of the bacteria during degradation of Escravos light crude oil ranged between 0.0037 and 0.0505 h-1, while that of the mixed cultures varied from 0.0144 to 0.1301 h-1. The crude oil was biodegraded by between 28.71% and 99.01% for single cultures and between 12.38% and 91.58% for the mixed cultures. Although specific growth rate and biomass were important at the initial stages of biodegradation, there was no significant correlation between growth rate and biomass and the extent of biodegradation of Escravos light crude oil.
We investigated the production of galactooligosaccharides (GOS) from lactose by alginate-immobilized cells of Sporobolomyces singularis YIT 10047 (IM-SS). β-Galactosidase activity was stable at 30 to 50°C but decreased dramatically between 50 and 60°C and disappeared at 70°C in acetate buffer. The enzyme activity remaining was no more than 20% of that of unheated samples after incubation in distilled water at 55°C, whereas its value was about 60% at the same temperature under buffered condition. However, activity was maintained more than 80% with 10% to 50% (w/w) lactose after incubation at 55°C without buffer. In a single-batch reaction, GOS yield was 41.0% with free cells and 40.4% with IM-SS. We attempted a repeated-batch reaction using IM-SS with 600 g L-1 lactose. IM-SS produced GOS stably for 20 batches (22 h/batch, 440 h in total) at 55°C and pH 5.0 or 6.0. IM-SS produced GOS at 242 g L-1, at a rate of 8.72 g L-1 h-1. Both GOS yield and production rate were higher than those in published experiments on GOS production using immobilized biocatalysts. The repeated-batch reaction with IM-SS would be an ideal system for GOS production because of its stability and high productivity.
Aspergillus sp. N2 and Penicillium sp. N3 are chromate-resistant filamentous fungi that were isolated from Cr(VI) contaminated soil based on their ability to decrease hexavalent chromium levels in the growth medium. After 120 h of growth in a medium containing 50 ppm Cr(VI) at near neutral pH, Aspergillus sp. N2 reduced the Cr(VI) concentration by about 75%. Penicillium sp. N3 was able to reduce the Cr(VI) concentration by only 35%. However, Penicillium sp. N3 reduced the Cr(VI) concentration in the medium by 93% under acidic conditions. Interestingly, the presence of Cu(II) enhanced the Cr(VI) reducing ability of Aspergillus sp. N2 and Penicillium sp. N3 at near neutral pH. Aspergillus sp. N2 and Penicillium sp. N3 reduced the Cr(VI) concentration in the growth medium to a virtually undetectable level within 120 h. For both Aspergillus sp. N2 and Penicillium sp. N3, mycelial seed cultures were more efficient at Cr(VI) reduction than conidium seed cultures. The mechanisms of Cr(VI) reduction in Aspergillus sp. N2 and Penicillium sp. N3 were enzymatic reduction and sorption to mycelia. Enzymatic activity contributed significantly to Cr(VI) reduction. Aspergillus sp. N2 and Penicillium sp. N3 reduced the levels of Cr(VI) in polluted soil samples, suggesting that these strains might be useful for cleaning up chromium-contaminated sites.