Evolution of Protein Molecules

Environmental applications for biosurfactants

The moderately halophilic heterotrophic aerobic bacteria form a diverse group of microorganisms. The property of halophilism is widespread within the bacterial domain. Bacterial halophiles are abundant in environments such as salt lakes, saline soils, and salted food products. Most species keep their intracellular ionic concentrations at low levels while synthesizing or accumulating organic solutes to provide osmotic equilibrium of the cytoplasm with the surrounding medium. Complex mechanisms of adjustment of the intracellular environments and the properties of the cytoplasmic membrane enable rapid adaptation to changes in the salt concentration of the environment. Approaches to the study of genetic processes have recently been developed for several moderate halophiles, opening the way toward an understanding of haloadaptation at the molecular level. The new information obtained is also expected to contribute to the development of novel biotechnological uses for these organisms.

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Biology of moderately halophilic aerobic bacteria

The process of microbial mineral plugging in porous media is common in nature. We examined physical and biochemical properties of CaCO3 precipitation induced by Bacillus pasteurii, an alkalophilic soil microorganism. X-ray diffraction analysis quantified the composition of the mineral deposited in sand and identified the CaCO3 crystal as calcite. Examination by scanning electron microscopy identified bacteria in the middle of calcite crystals, which acted as nucleation sites. The rate of microbiological CaCO3 precipitation correlated with cell growth and was significantly faster than that of chemical precipitation. Biochemical properties of urease (urea amidohydrolase, E.C. 3.5.1.5) from B. pasteurii that was indirectly involved in CaCO3 precipitation were examined to understand the kinetics of the microbiological process. Urease from B. pasteurii exhibited a relatively low affinity for urea at pH 7.0 with a Km of 41.6 mM and Vmax of 3.55 mM min−1 mg−1 protein and increased affinity at pH 7.7 with a Km of 26.2 mM and Vmax of 1.72 mM min−1 mg−1 protein. Results of kinetic studies indicate that urease activity and its affinity to urea are significantly high at the pH where calcite precipitation is favorable. Our findings further suggest a potential use of the microbial calcite precipitation process in remediation of the surface and subsurface of porous media.

Microbiological precipitation of CaCO3

Taxonomy relies on three key elements: characterization, classification and nomenclature. All three elements are dynamic fields, but each step depends on the one which precedes it. Thus, the nomenclature of a group of organisms depends on the way they are classified, and the classification (among other elements) depends on the information gathered as a result of characterization. While nomenclature is governed by the Bacteriological Code, the classification and characterization of prokaryotes is an area that is not formally regulated and one in which numerous changes have taken place in the last 50 years. The purpose of the present article is to outline the key elements in the way that prokaryotes are characterized, with a view to providing an overview of some of the pitfalls commonly encountered in taxonomic papers.

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Notes on the characterization of prokaryote strains for taxonomic purposes.

Summary: A study was made of 516 randomly selected isolates of moderately halophilic bacteria from solar salterns showing salinities between 8.8 and 40.0% (w/v) total salts, located in S.E. Spain. After purification, many cytological, physiological, biochemical, nutritional and antibiotic sensitivity characters were determined for 106 selected saltern isolates and two reference strains. Data were coded and analysed by numerical techniques using the Jaccard coefficient (S j), and clusters of strains were obtained by average linkage (UPGMA) analysis. Nine major phenons were found at the 72.5% similarity level. The properties of each phenon are given, their taxonomic affinities are discussed, and typical reference strains are suggested. Almost all the strains were related to genera known to contain marine species. A large number of the strains could be tentatively assigned to the genus Vibrio, suggesting that this may be an abundant taxon of moderately halophilic Gram-negative rods in solar salterns.

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Numerical Taxonomy of Moderately Halophilic Gram-negative Rods

http://dzumenvis.nic.in/Taxonomy/pdf/A%20Detailed%20Phenotypic%20Characterisation.pdf

A Detailed Phenotypic Characterisation of the Type Strains of Halomonas Species

Two Gram-positive, endospore-forming bacterial strains, CR-502T and CR-14b, which produce surfactant molecules are described. Phenotypic tests and phylogenetic analyses showed these strains to be members of the genus Bacillus and related to the species Bacillus atrophaeus, Bacillus mojavensis, Bacillus subtilis, Bacillus vallismortis and Bacillus amyloliquefaciens, although they differ from these species in a number of phenotypic characteristics. DNA-DNA hybridization confirmed that they show less than 20 % hybridization with the above-mentioned species and therefore represent a novel species of Bacillus. The DNA G+C content is 46.4 mol% in strain CR-502T and 46.1 mol% in strain CR-14b. The main fatty acids in strain CR-502T are 15 : 0 anteiso (32.70 %), 15 : 0 iso (29.86 %) and 16 : 0 (13.41 %). The main quinone in strain CR-502T is MK-7 (96.6 %). In the light of the polyphasic evidence gathered in this study, it is proposed that these strains be classified as a novel species of the genus Bacillus, with the name Bacillus velezensis sp. nov. The type strain (CR-502T=CECT 5686T=LMG 22478T) was isolated from a brackish water sample taken from the river Velez at Torredelmar in Malaga, southern Spain.

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Bacillus velezensis sp. nov., a surfactant-producing bacterium isolated from the river Vélez in Málaga, southern Spain

Mauran is an anionic, sulfated heteropolysaccharide with a high uronic-acid content, synthesized by strain S-30 of the halophilic bacterium Halomonas maura Under optimum environmental and nutritional conditions, it is capable of producing up to 38 g of mauran per liter of medium Aqueous solutions of mauran are highly viscous and display pseudoplastic, viscoelastic and thixotropic behavior Its viscosity is stable over a wide pH range (3–11), after freezing-thawing processes, and in the presence of sucrose, salts, surfactants and α-hydroxyl acids It has a high capacity for binding lead and other cations Its molecular mass when collected from an MY medium supplemented with 25% w/v salt during the stationary growth phase is 47×106 Da

Mauran, an exopolysaccharide produced by the halophilic bacterium Halomonas maura, with a novel composition and interesting properties for biotechnology.

Deleya halophila sp. nov., which was isolated from hypersaline soils, is proposed. Each of 38 isolates, together with 8 reference strains, was examined in 97 phenotypic tests, and the data were analyzed by numerical taxonomy procedures. The 38 isolates formed a distinct group at a 76% similarity value, as determined by an analysis performed with the simple matching coefficient and unweighted average linkage clustering. Characteristically, the isolates were aerobic, gram-negative rods that were motile by one to eight peritrichous flagella. They grew optimally in the presence of 7.5% (wt/vol) marine salts. The distinguishing features of the new species are its salt requirement, biochemical features, and nutritional versatility. The guanine-plus-cytosine content of the deoxyribonucleic acid is 66.7 mol%. The type strain of this species is strain F5–7 (= CCM 3662).

Emilia Quesada

Papers

Numerical Taxonomy of Moderately Halophilic Gram-negative Rods

A Detailed Phenotypic Characterisation of the Type Strains of Halomonas Species

Bacillus velezensis sp. nov., a surfactant-producing bacterium isolated from the river Vélez in Málaga, southern Spain

Mauran, an exopolysaccharide produced by the halophilic bacterium Halomonas maura, with a novel composition and interesting properties for biotechnology.

Deleya halophila, a New Species of Moderately Halophilic Bacteria