Biomedical subjects

V V Kevbrin

Publications and source records attributed to V V Kevbrin.

5 recordsLinked to original sources

PubMed2005

Cellulase activity of a haloalkaliphilic anaerobic bacterium, strain Z-7026.

The cellulolytic activity of an alkaliphilic obligate anaerobic bacterium, Z-7026, which was isolated from the microbial community of soda-lake sediments and belongs to the cluster III of Clostridia with low G+C content, was studied. The bacterium was capable of growing in media with cellulose or cellobiose as the sole energy sources. Its maximal growth rate on cellobiose (0.042-0.046 h(-1)) was observed at an initial pH value of 8.5-9.0, whereas the maximal rate of cellulase synthesis, assayed by using a novel fluorimetric approach, was found to be 0.1 h(-1) at pH 8-8.5. Secreted proteins revealed high affinity for cellulose and were represented by two major forms of molecular masses of 75 and 84 kDa, whereas the general protein composition of the precipitated and cellulose-bound preparations was similar to cellulosome subunits of Clostridium thermocellum. The optimum pH of the partially purified enzyme preparation towards both amorphous and crystalline cellulose was in the range 6-9, with more than 70% and less than 50% of maximal activity being retained at pH 9.2 and 5.0, respectively.

Bacteria, Anaerobic↗

PubMed2004

Alkalithermophiles.

Alkalithermophiles are an exciting subset of extremophilic organisms and represent extremophiles that are adapted to two extreme conditions, i.e. to a combination of alkaline and thermobiotic growth conditions. Among the anaerobic alkalithermophiles are representatives of both Bacteria and Archaea within a wide variety of physiological types and systematic groups, although a great majority belongs to the Firmicutes. Alkaliphiles have been isolated from a variety of niches including mesobiotic and neutrophilic soils and sediments. Interestingly anaerobic isolates from mesobiotic and neutrophilic niches exhibit shorter doubling times than isolates from thermobiotic niches; some anaerobic alkalithermophiles exhibit extremely fast growth rates, i.e. doubling times as short as 10 min. Their adaptation to both high pH and high temperature draws our attention not only because they are potential sources of industrially valuable enzymes but also because of their adaptive mechanisms to external environmental parameters. They could thus function as model organisms for extraterrestrial life in some environments and for theories on the origin of life. Alkalithermophiles, as far we know, do not represent the most thermophilic nor the most alkaliphilic of micro-organisms but represent the most alkaliphilic ones among the thermophiles and vice versa. We believe that the presently known species are only the tip of the iceberg and therefore that they do not represent the true boundaries under which life can thrive in respect to high temperature in alkaline environments.

Archaea↗

PubMed1998

Tindallia magadii gen. nov., sp. nov.: an alkaliphilic anaerobic ammonifier from soda lake deposits.

Strain Z-7934, an alkaliphilic, obligately anaerobic, fermentative, asporogenous bacterium with Gram-positive cell wall structure, was isolated from soda deposits in Lake Magadi, Kenya. The organism ferments only a few amino acids, preferentially arginine and ornithine, with production of acetate, propionate, and ammonia. It is a true alkaliphile, with pH range for growth ranging from 7.5 to 10.5 (optimum pH 8.5), and growth is dependent on the presence of sodium ions. The G+C content of the genomic DNA is 37.6 mol%. 16S rDNA sequence analysis of strain Z-7934 shows that it belongs phylogenetically to cluster XI of the low G+C Gram-positive bacteria. On the basis of its distinct phylogenetic position and unique physiological properties, we propose a new genus and new species, Tindallia magadii, for this strain. The type strain is Z-7934(T) (=DSM 10318).

Alkalies↗

PubMed1996

Spirochaeta alkalica sp. nov., Spirochaeta africana sp. nov., and Spirochaeta asiatica sp. nov., alkaliphilic anaerobes from the Continental Soda Lakes in Central Asia and the East African Rift.

During a study of microbial communities in athalassic bodies of water, three new species within the genus Spirochaeta were described. These are alkaliphilic Spirochaeta alkalica sp. nov. Z-7491 (DSM 8900) and halophilic S. africana sp. nov. Z-7692 (DSM 8902) from the soda-depositing Lake Magadi in Central Africa and haloalkaliphilic S. asiatica sp. nov. Z-7591 (DSM 8901) from Lake Khatyn, Central Asia. These mesophilic spirochetes develop at pHs of > 9 as anaerobic saccharolytic dissipotrophs. The DNA base compositions (moles percent G+C) of the strains were as follows: S. alkalica Z-7491, 57.1; S. africana Z-7692, 56.1; and S. asiatica Z-7591, 49.2. The optimum growth parameters (temperature, pH, and NaCl concentration [percent, wt/vol], respectively) were as follows: for S. alkalica Z-7491, 35 degrees C, 9.2, and 5 to 7%; for S. africana Z-7692, 35 degrees C, 9.3, and 5 to 7%; and for S. asiatica Z-7591, 35 degrees C, 8.9, and 3 to 6%. The products of glucose fermentation were acetate, hydrogen, ethanol, and lactate, in different proportions, for S. alkalica and S. africana; for S. asiatica, they were acetate, ethanol, and lactate. S. asiatica is strictly anaerobic, while S. alkalica and S. africana are rather aerotolerant. All three species group within the radiation of the majority of the species of the genus Spirochaeta. Studies of the genes encoding 16S rRNA indicate a possible fanning out of the phylogenetic tree of spirochetes.

Africa, Eastern↗

PubMedDate not supplied

[Clostridium alkalicellum sp. nov., an obligately alkaliphilic cellulolytic bacterium from a soda lake in the Baikal region].

The first anaerobic alkaliphilic cellulolytic microorganism has been isolated from the Verkhnee Beloe soda lake (Buryatiya, Russia) with pH 10.2 and a salt content of up to 24 g/l. Five strains were characterized. Strain Z-7026 was chosen as the type strain. The cells of the isolate are gram-positive spore-forming rods. A mucous external capsule is produced. The microorganism is obligately alkaliphilic, growing in a pH range of 8.0-10.2, with an optimum at pH 9.0. Sodium ions and, in carbonate-buffered media, sodium chloride are obligately required. The microorganism is slightly halophilic; it grows at 0.017-0.4 M Na+ with an optimum at 0.15-0.3 M Na+. The metabolism is fermentative and strictly anaerobic. Cellulose, cellobiose, and xylan can be used as growth substrates. Plant and algal debris can be fermented. Lactate, ethanol, acetate, hydrogen, and traces of formate are produced during cellulose or cellobiose fermentation. Yeast extract or vitamins are required for anabolic purposes. The microorganism fixes dinitrogen and is nitrogenase-positive. It is tolerant to up to 48 mM Na2S. Growth is not inhibited by kanamycin or neomycin. Chloramphenicol, streptomycin, penicillin, ampicillin, ampiox, bacillin, novobiocin, and bacitracin suppress growth. The DNA G+C content is 29.9 mol %. According to the nucleotide sequence of its 16S rRNA gene, strain Z-7026 is phylogenetically close to the neutrophilic cellulolytic bacteria Clostridium thermocellum (95.5%), C. aldrichii (94.9%), and Acetivibrio cellulolyticus (94.8%). It is proposed as a new species: Clostridium alkalicellum sp. nov.

Anaerobiosis↗