The Methanogens are a diverse group of organisms found in anaerobic environments such as anaerobic sludge digester, wet wood of trees, sewage, rumen, black mud, black sea sediments , etc which utilize carbon dioxide and hydrogen and produce methane. They are nutritionally fastidious anaerobes with the redox potential below -300 mV and usually grow at pH range of 6.0-8.0 [1]. Substrates utilized for growth and methane production include hydrogen, formate, methanol, methylamine, acetate, etc. They metabolize only restricted range of substrates and are poorly characterized with respect to other metabolic, biochemical and molecular properties.

No abstract

Forty-three indigenous arsenic resistant bacteria were isolated from arsenic rich soil of Rajnandgaon district in the state of Chhattisgarh, India by enrichment culture technique. Among the isolates, two of the bacteria (As-9 and As-14) exhibited high resistance to As(V) [MIC ≥ 700 mM] and As(III) [MIC ≥ 10 mM] and were selected for further studies. Both these bacteria grew well in the presence of arsenic [20 mM As(V) and 5 mM As(III)], but the isolate As-14 strictly required arsenic for its survival and growth and was characterized as a novel arsenic dependent bacterium. The isolates contributed to 99% removal of arsenic from the growth medium which was efficiently accumulated in the cell. Quantitative estimation of arsenic through Atomic Absorption Spectrophotometer revealed that there was >60% accumulation of both As(V) and As(III) by the two isolates. Scanning Electron Microscopic analysis showed a fourfold increase in bacterial cell volume when grown in the presence of arsenic and the results of Transmission Electron Microscopy and energy-dispersive X-ray spectroscopy proved that such an alteration was due to arsenic accumulation. Such arsenic resistant bacteria with efficient accumulating property could be effectively applied in the treatment of arsenic contaminated water.

During the recent years extensive efforts have been made to find out bacteriocins from lactic acid bacteria (LAB) active against various food spoilage and pathogenic bacteria, and superior stabilities against heat treatments and pH variations. Bacteriocins isolated from LAB have been grouped into four classes. Circular bacteriocins which were earlier grouped among the four groups of bacteriocins, have recently been proposed to be classified into a different class, making it class V bacteriocins. Circular bacteriocins are special molecules, whose precursors must be post translationally modified to join the N to C termini with a head-to-tail peptide bond. Cyclization appears to make them less susceptible to proteolytic cleavage, high temperature and pH, and, therefore, provides enhanced stability as compared to linear bacteriocins. The advantages of circularization are also reflected by the fact that a significant number of macrocyclic natural products have found pharmaceutical applications. Circular bacteriocins were unknown two decades ago, and even to date, only a few circular bacteriocins from a diverse group of Gram positive organisms have been reported. The first example of a circular bacteriocin was enterocin AS-48, produced by Enterococcus faecalis AS-48. Gassereccin A, produced by Lactobacillus gasseri LA39, Reutericin 6 produced by Lactobacillus reuteri LA6 and Circularin A, produced by Clostridium beijerinickii ATCC 25,752, are further examples of this group of antimicrobial peptides. In the present scenario, Gassericin A can be an important tool in the food preservation owing to its properties of high pH and temperature tolerance and the fact that it is produced by LAB L. gasseri, whose many strains are proven probiotic.

No abstract

No abstract

A reuterin (3-hydroxypropinaldehyde, 3-HPA)-producing isolate from a human infant fecal sample was identified as Lactobacillus reuteri BPL-36 strain. The organism displayed a broad-spectrum antimicrobial activity. The gene (gdh) encoding a glycerol dehydratase subunit was detected by PCR, thus confirming its reuterin-producing ability. Reuterin concentration of 89.63 mM/mL was obtained in the MRS-glycerol medium after 16 h of incubation at 37 °C. The reuterin concentration required to inhibit the growth of Pseudomonas aeruginosa, Escherichia coli O157: H7, Salmonella typhi, Staphylococcus aureus, and Listeria monocytogenes was found to be 1.0, 2.0, 2.0, 4.0, and 10.0 AU/mL, respectively. Antimicrobial efficiency test using BPL-36 cell-free supernatant co-incubated along with different test pathogens was done. Viability of all the tested pathogens decreased with increasing contact time with the cell-free supernatant. S. typhi was observed to be the most susceptible among the tested organisms, and the number of viable cells hugely declined as the contact with cell-free supernatant continued, resulting in a reduction of 6 log cycles (100 % inhibition) of the cells after 4 h of treatment. Production of biogenic amines and degradation of mucin by the reuterin-producing BPL-36 strain were not detected.

No abstract