Biological treatment of tannery wastewater by using salt-tolerant bacterial strains

Background  

High salinity (1–10% w/v) of tannery wastewater makes it difficult to be treated by conventional biological treatment. Salt tolerant microbes can adapt to these saline conditions and degrade the organics in saline wastewater.     

Homepeptide Repeats:Implications for Protein Structure,Function and Evolution

Analysis of protein sequences from Mycobacterium tuberculosis H37Rv(Mtb H37Rv) was performed to identify homopeptide repeatcontaining proteins(HRCPs).Functional annotation of the HRCPs showed that they are preferentially involved in cellular metabolism.Furthermore,these homopeptide repeats might play some specific roles in protein-protein interaction.Repeat length differences among Bacteria,Archaea and Eukaryotes were calculated in order to identify the conservation of the repeats in these divergent kingdoms.From the results,it was evident that these repeats have a higher degree of conservation in Bacteria and Archaea than in Eukaryotes.In addition,there seems to be a direct correlation between the repeat length difference and the degree of divergence between the species.Our study supports the hypothesis that the presence of homopeptide repeats influences the rate of evolution of the protein sequences in which they are embedded.Thus,homopeptide repeat may have structural,functional and evolutionary implications on proteins.     

Structural analysis of NADPH depleted bovine liver catalase and its inhibitor complexes

To study the functional role of NADPH during mammalian catalase inhibition, the X-ray crystal structures of NADPH-depleted bovine liver catalase and its inhibitor complexes, cyanide and azide, determined at 2.8Å resolution. From the complex structures it is observed that subunits with and without an inhibitor/catalytic water molecule are linked by N-terminal domain swapping. Comparing mammalian- and fungal- catalases, we speculate that NADPH-depleted mammalian catalases may function as a domain-swapped dimer of dimers, especially during inactivation by inhibitors like cyanide and azide. We further speculate that in mammalian catalases the N-terminal hinge-loop region and α-helix is the structural element that senses NADPH binding. Although the above arguments are speculative and need further verification, as a whole our studies have opened up a new possibility, viz. that mammalian catalase acts as a domain-swapped dimer of dimers, especially during inhibitor binding. To generalize this concept to the formation of the inactive state in mammalian catalases in the absence of tightly bound NADPH molecules needs further exploration. The present study adds one more intriguing fact to the existing mysteries of mammalian catalases.     

Media replenishment: A tool for the analysis of high-cell density perfusion systems

A simple method to analyze media consumption and by-product build-up in high-cell-density perfusion cultures has been developed. This technique makes use of media replenishment strategy which can be used to decouple the two phenomena. Also, the replenished media method can be used to identify limitation by complex and undefined media components such as bovine serum.     

Anin vitro test using cholesterol metabolism of macrophages to determine drug sensitivity and resistance ofMycobacterium leprae

Macrophages that have ingested liveMycobacterium leprae show a preferential accumulation of cholesterol ester. Such an accumulation is not seen, on the ingestion of dead bacteria. Among the macrophages that ingest liveMycobacterium leprae, the presence of dapsone or rifampicin prevents largely the alteration in the anticipated increase in the cholesterol ester indicating the sensitivity of the bacteria to the drug. In the small number of relapsed patients, the presence of dapsone did not reduce the cholesterol ester increase, suggesting that theMycobacterium leprae present are either resistant or escaped detection. The method provides a rapid drug screening system foranti-Mycobacterium leprae activity of known and unknown compounds     

Importance of determining viability ofMycobacterium leprae inside macrophages—anin vitro method using uracil

It has been demonstrated thatMycobacterium leprae, are caPable of taking uP uracil and incorPorating it into trichloroacetic acid-insoluble materials, both as free susPension of bacteria, as well as when they are inside the macrophages, a host cell for theirin vivo survival. Same amount of bacteria show better incorPoration inside macroPhages than as free bacterial susPension. Both tyPes of incorPoration are inhibited by rifamPicin an antileProsy drug and an RNA synthesis inhibitor. Thus uracil uPtake byMycobacterium lePrae inside macroPhages has been used for standardising a raPidin vitro viability assay for the leProsy causing bacteria.     

The Bay of Bengal exposes abundant photosynthetic picoplankton and newfound diversity along salinity-driven gradients

The Bay of Bengal (BoB) is a 2,600,000 km² expanse in the Indian Ocean upon which many humans rely. However, the primary producers underpinning food chains here remain poorly characterized. We examined phytoplankton abundance and diversity along strong BoB latitudinal and vertical salinity gradients—which have low temperature variation (27–29°C) between the surface and subsurface chlorophyll maximum (SCM). In surface waters, Prochlorococcus averaged 11.7 ± 4.4 × 10⁴ cells ml⁻¹, predominantly HLII, whereas LLII and ‘rare’ ecotypes, HLVI and LLVII, dominated in the SCM. Synechococcus averaged 8.4 ± 2.3 × 10⁴ cells ml⁻¹ in the surface, declined rapidly with depth, and population structure of dominant Clade II differed between surface and SCM; Clade X was notable at both depths. Across all sites, Ostreococcus Clade OII dominated SCM eukaryotes whereas communities differentiated strongly moving from Arabian Sea-influenced high salinity (southerly; prasinophytes) to freshwater-influenced low salinity (northerly; stramenopiles, specifically, diatoms, pelagophytes, and dictyochophytes, plus the prasinophyte Micromonas) surface waters. Eukaryotic phytoplankton peaked in the south (1.9 × 10⁴ cells ml⁻¹, surface) where a novel Ostreococcus was revealed, named here Ostreococcus bengalensis. We expose dominance of a single picoeukaryote and hitherto ‘rare’ picocyanobacteria at depth in this complex ecosystem where studies suggest picoplankton are replacing larger phytoplankton due to climate change.     

Reversion of anE. coli strain carrying an IS1-activatedbgl operon under nonselective conditions is predominantly due to deletions within the structural genes

Thebgl operon ofEscherichia coli, which encodes the genes necessary for transport and catabolism of β-glucosides, is silent in wild-type cells and is activated by the transposition of IS elements. The silent form of the operon appears to be the stable state. We isolated Bgl^- revertants of an activated strain after growth under nonselective conditions to understand whether activation of the cryptic operon by IS elements is reversible. Genetic and molecular analyses revealed that a majority of revertants carry deletions of thebgl structural genes, indicating that an irreversible alteration has occurred in the operon. Implications of these results for the evolution and maintenance of cryptic genes are discussed. [Yakkundi A., Moorthy S. and Mahadevan S. 1998 Reversion of anE. coli strain carrying an IS1-activatedbgl operon under nonselective conditions is predominantly due to deletions within the structural genes.J. Genet. 77, 21–26]