Proteobacteria, extremophiles and unassigned species dominate in a tape-like showerhead biofilm

The development of showerhead biofilms exposes the user to repeated contact with potentially pathogenic microbes, yet we know relatively little about the content of these aggregates. The aim of the present study was to examine the microbial content of tape-like films found protruding from a domestic showerhead. Culturing showed that the films were dominated by aerobic - and -proteobacteria. Three isolates made up almost the entire plate count. These were a Brevundimonas species, a metalophilic Cupriavidus species and a thermophile, Geobacillus species. Furthermore, it was shown that the Cupriavidus isolate alone had a high capacity for biofilm formation and thus might be the initiator of biofilm production. A clone library revealed the same general composition. However, half of the 70 clones analyzed could not be assigned to a particular bacterial phylum and of these 29 differed from one another by only 12 base pairs, indicating a single species. Thus both the culture dependent and culture independent characterizations suggest a simple yet novel composition. The work is important as the biofilm is fundamentally different in form (tape-like) and content from that of all previously reported ones, where variously Mycobacterium, Methylobacterium and Xanthomonas species have dominated, and extremophiles were not reported.(AU)

Bioprospecting thermophiles for cellulase production: a review

Most of the potential bioprospecting is currently related to the study of the extremophiles and their potential use in industrial processes. Recently microbial cellulases find applications in various industries and constitute a major group of industrial enzymes. Considerable amount of work has been done on microbial cellulases, especially with resurgence of interest in biomass ethanol production employing cellulases and use of cellulases in textile and paper industry. Most efficient method of lignocellulosic biomass hydrolysis is through enzymatic saccharification using cellulases. Significant information has also been gained about the physiology of thermophilic cellulases producers and process development for enzyme production and biomass saccharification. The review discusses the current knowledge on cellulase producing thermophilic microorganisms, their physiological adaptations and control of cellulase gene expression. It discusses the industrial applications of thermophilic cellulases, their cost of production and challenges in cellulase research especially in the area of improving process economics of enzyme production.

Characterization and stability of extracellular alkaline proteases from halophilic and alkaliphilic bacteria isolated from saline habitat of coastal Gujarat, India

The present study deals with the isolation and characterization of the moderately halophilic-alkaliphilic bacteria from a saline habitat in western India. Eight different bacterial strains were isolated using enrichment techniques at 20% (w/v) NaCl and pH 10. The isolates exhibited diversity towards gram's reaction, colony and cell morphology. They were able to grow and produce alkaline protease over a broad range of NaCl, 5-20% (w/v) and pH, 8-10. None of the isolates could grow at pH 7, and one could not grow even at pH 8. Crude and partially purified proteases from strain S5 were subjected to characterization with reference to pH, salt stability and protein folding. Optimum protease activity and stability was recorded at 10% salt and pH 9-9.5. Denaturation kinetics of S5 alkaline protease along with a reference protease was studied at 8M urea followed by renaturation. The S5 alkaline protease could be partially renatured up to 32% of the original activity. Despite of the fact that all the 8 isolates were from the same site, they displayed significant diversity with respect to their salt requirement for growth and enzyme secretion. While the effect of pH was less demarcated on growth, the protease production was significantly affected. Isolate S5 produced substantial amount of halotolerant and alkaline protease. The activity and stability of the alkaline protease in a broader range of pH and salt would definitely make this enzyme an important candidate for various industrial applications.

O presente estudo relata o isolamento e caracterização de bactérias moderadamente halofilicas e alcalífilicas de um habitat salino no oeste da Índia. Oito cepas diferentes de bactérias foram isoladas empregando técnicas de enriquecimento em NaCl a 20% (p/v) e pH 10. As cepas apresentaram diversidade em relação à coloração de Gram e à morfologia das colônias e células. As cepas foram capazes de multiplicar e produzir protease alcalina em uma ampla faixa de concentração de NaCl (5 a 20%) e pH (8 a 10). Nenhuma das cepas foi capaz de se multiplicar em pH 7, e uma não se multiplicou nem em pH 8.0. Proteases naturais e parcialmente purificadas da cepa S5 foram submetidas à caracterização com relação ao pH, estabilidade salina, e estrutura protéica. Atividade e estabilidade ótimas da protease foram obtidas com 10% de sal e pH 9-9,5. A cinética de denaturação da protease de S5, juntamente com uma protease de referencia, foi avaliada com uréia 8M seguida de renaturação. A protease alcalina de S5 foi renaturada a 32% da atividade original. Apesar de provenientes do mesmo local, as oito cepas mostraram grande diversidade em relação à exigência de sal para multiplicação e secreção enzimática. Enquanto o efeito do pH na multiplicação foi menos marcante, o efeito na produção de protease foi significativamente afetada. A cepa S5 produziu uma quantidade substancial de protease alcalina e halotolerante. A atividade e estabilidade da protease alcalina em uma faixa mais ampla de pH e sal tornam essa enzima uma importante candidata para diversas aplicações industriais.