Journal of Basic Microbiology

Microbial polysaccharides are multifunctional and can be divided into intracellular polysaccharides, structural polysaccharides and extracellular polysaccharides or exopolysaccharides (EPS). Extracellular polymeric substances (EPS), produced by both prokaryotes (eubacteria and archaebacteria) and eukaryotes (phytoplankton, fungi, and algae), have been of topical research interest. Newer approaches are carried out today to replace the traditionally used plant gums by their bacterial counterparts. The bacterial exopolysaccharides represent a wide range of chemical structures, but have not yet acquired appreciable significance. Chemically, EPS are rich in high molecular weight polysaccharides (10 to 30 kDa) and have heteropolymeric composition. They have new‐fangled applications due to the unique properties they possess. Owing to this, exopolysaccharides have found multifarious applications in the food, pharmaceutical and other industries. Hence, the present article converges on bacterial exopolysaccharides. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Nowadays, many researches have been made on gallotannin biodegradation and have gained great success in further utilization. Some of industrial applications of these findings are in the production of tannase, the biotransformation of tannic acid to gallic acid or pyrogallol and detannification of food and fodder. Although ellagitannins have the typical C–C bound which is more difficult to be degraded than gallotannins, concerted efforts are still in progress to improve ellagitannin degradation and utilization. Currently, more attention is mainly focused on intestinal microflora biodegradation of tannins especially ellagitannins which can contribute to the definition of their bioavailability for both human beings and ruminants. Also there have been endeavours to utilize the tannin‐degrading activity of different fungi for ellagitannin‐rich biomass, which will facilitate application of tannin‐degrading enzymes in strategies for improving industrial and livestock production. Due to the complicated structures of complex tannins and condensed tannins, the biodegradation of them is much more difficult and there are fewer researches on them. Therefore, the researches on the mechanisms of gallotannin and ellagitannin biodegradation can result in the overall understanding to the biodegradation of complex tannins and condensed tannins. Biodegradation of tannins is in an incipient stage and further studies have to be carried out to exploit the potential of various tannins for largescale applications in food, fodder, medicine and tannery effluent treatment. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Deoxynivalenol (DON) is a trichothecene secondary metabolite produced by Fusarium species infecting cereal crops. As a mycotoxin, DON causes losses in livestock production and poses a health risk to humans consuming contaminated cereal products. DON also acts as a virulence factor, facilitating the colonization of host plants by Fusarium spp. Enzymatic detoxification of mycotoxins in feed additives and genetically modified crops is a promising approach for the reduction of mycotoxin contamination of feeds and food. A prerequisite for the developoment of biotechnological strategies for DON detoxification is the availability of genes encoding suitable enzymatic activities. With the goal of isolating microbial cultures that can be used as a source of such activies, we screened 1285 microbial cultures from farmland soil, cereal grains, insects and other sources for DON transformation under aerobic conditions. One mixed culture transformed DON into two chromatographically separable products. The main product of the transformation was purified and its structure was elucidated by mass spectroscopy, ¹H‐NMR, ¹³C‐NMR and proton‐proton and carbon‐proton correlated NMR spectroscopy. The structure of this product was determined to be 3‐keto‐4‐deoxynivalenol. The DON‐transforming mixed culture survived and retained its transforming activity during a starvation period of six months at 20 °C. Transformation of DON was suppressed by low concentrations of glucose and high concentrations of tryptone and yeast extract. Cell‐free supernatants obtained either by filtration through a 0.22 μm membrane filter or by centrifugation did not exert DON‐transforming activity. Trichothecenes 15‐acetyl‐DON, 3‐acetyl‐DON and fusarenon‐X were also transformed. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The genetic diversity of 29 endophytic bacterial strains isolated from apoplastic sap of the medullary parenchym of the stem of healthy sugarcane plants grown in Cuba was analysed by Two Primers‐Ramdom Amplified Polymorphic DNA fingerprinting (TP‐RAPD) and 16S rRNA gene sequencing. The strains were distributed into 17 groups on the basis of their TP‐RAPD patterns, and a representative strain from each group was subjected to 16S rRNA gene sequencing. Analysis of these sequences showed that the isolates belong to a wide variety of phylogenetic groups being closely related to species of genera Bacillus and Staphylococcus from Firmicutes, Microbacterium, Micrococcus and Kokuria from Actinobacteria, Rhizobium and Gluconacetobacter from α ‐Proteobacteria, Comamonas and Xanthomonas from β ‐Proteobacteria, and Acinetobacter and Pantoea from γ ‐Proteobacteria. These results show the complexity of the bacterial populations present in inner tissues of sugarcane, and indicate the interest and relevance of the studies on microbial diversity to improve our knowledge on the plant endophytic bacterial communities. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Under aerobic conditions, the culturable microbial population of acidic forest soils was more tolerant to acidic cultivation conditions than was the culturable microbial population of less acidic soils. The number of culturable bacteria decreased sharply under acidic cultivation conditions, while the number of culturable fungi remained relatively constant over the pH range 2.2–6.5. The ratios of culturable bacteria to culturable fungi were greater than one at pH 6.5; in contrast, the bacteria‐to‐fungi ratios were less than one at pH 2.2–4. At pH's approximating those of the soils examined, culturable fungi predominated the culturable microbial community in acidic soils. However, relative to the populations resolved, acidic forest soils displayed a more acid tolerant bacterial population than did less acidic forest soils. The culturable fungal population contained both filamentous and yeast morphologies. An acid‐tolerant fungal isolate that grew at pH 1 was identified as a subspecies of Penicillium frequentans, and an acid‐tolerant yeast that grew at pH 2 was identified as the yeast stage of the basidiomycetes Ustilago maydis.

The filamentous fungus Aspergillus ochraceus NCIM‐1146 was found to degrade kerosene, when previously grown mycelium (96 h) was incubated in the broth containing kerosene. Higher levels of NADPH‐DCIP reductase, aminopyrine N‐demethylase and kerosene biodegradation activities were found to be present after the growth in potato dextrose broth for 96 h, when compared with the activities at different time intervals during the growth phase. NADPH was the preferred cofactor for enzyme activity, which was inhibited by CO, indicating cytochrome P450 mediated reactions. A significant increase in all the enzyme activities was observed when mycelium incubated for 18 h in mineral salts medium, containing cholesterol, camphor, naphthalene, 1,2‐dimethoxybenzene, phenobarbital, n‐hexane, kerosene or saffola oil as inducers. Acetaldehyde produced by alcohol dehydrogenase could be used as an indicator for the kerosene biodegradation. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)