Recombination drives genetic diversification of Streptococcus dysgalactiae subspecies equisimilis in a region of streptococcal endemicity.

Infection of the skin or throat by Streptococcus dysgalactiae subspecies equisimilis (SDSE) may result in a number of human diseases. To understand mechanisms that give rise to new genetic variants in this species, we used multi-locus sequence typing (MLST) to characterise relationships in the SDSE population from India, a country where streptococcal disease is endemic. The study revealed Indian SDSE isolates have sequence types (STs) predominantly different to those reported from other regions of the world. Emm-ST combinations in India are also largely unique. Split decomposition analysis, the presence of emm-types in unrelated clonal complexes, and analysis of phylogenetic trees based on concatenated sequences all reveal an extensive history of recombination within the population. The ratio of recombination to mutation (r/m) events (11:1) and per site r/m ratio (41:1) in this population is twice as high as reported for SDSE from non-endemic regions. Recombination involving the emm-gene is also more frequent than recombination involving housekeeping genes, consistent with diversification of M proteins offering selective advantages to the pathogen. Our data demonstrate that genetic recombination in endemic regions is more frequent than non-endemic regions, and gives rise to novel local SDSE variants, some of which may have increased fitness or pathogenic potential.

Disease burden due to Streptococcus dysgalactiae subsp. equisimilis (group G and C streptococcus) is higher than that due to Streptococcus pyogenes among Mumbai school children.

Streptococcus pyogenes [group A streptococcus (GAS)], a human pathogen, and Streptococcus dysgalactiae subsp. equisimilis [human group G and C streptococcus (GGS/GCS)] are evolutionarily related, share the same tissue niche in humans, exchange genetic material, share up to half of their virulence-associated genes and cause a similar spectrum of diseases. Yet, GGS/GCS is often considered as a commensal bacterium and its role in streptococcal disease burden is under-recognized. While reports of the recovery of GGS/GCS from normally sterile sites are increasing, studies describing GGS/GCS throat colonization rates relative to GAS in the same population are very few. This study was carried out in India where the burden of streptococcal diseases, including rheumatic fever and rheumatic heart disease, is high. As part of a surveillance study, throat swabs were taken from 1504 children attending 7 municipal schools in Mumbai, India, during 2006-2008. GAS and GGS/GCS were identified on the basis of beta-haemolytic activity, carbohydrate group and PYR test, and were subsequently typed. The GGS/GCS carriage rate (166/1504, 11 %) was eightfold higher than the GAS carriage (22/1504, 1.5 %) rate in this population. The 166 GGS/GCS isolates collected represented 21 different emm types (molecular types), and the 22 GAS isolates represented 15 different emm types. Although the rate of pharyngitis associated with GGS/GCS is marginally lower than with GAS, high rates of throat colonization by GGS/GCS underscore its importance in the pathogenesis of pharyngitis.

A coupled photocatalytic-biological process for degradation of 1-amino-8-naphthol-3, 6-disulfonic acid (H-acid).

There has been growing emphasis on the development of coupled treatment systems (e.g., advanced oxidation-biological) for treating poorly biodegradable wastewater. An attempt has been made in the present study to couple photocatalytic (TiO2/UV) pretreatment with conventional activated sludge process to achieve improvement in the biodegradation of H-acid. The combination of titanium dioxide and UV light has been known to generate strong oxidants that degrade several organic pollutants into carbon dioxide via the formation of some intermediates. The intermediates formed may undergo biodegradation readily. Accordingly, photodegradation experiments were carried out initially at an optimized TiO2 dose and the minimum pretreatment time required for transforming H-acid was identified. For this purpose, UV-vis spectrophotometry and high-performance liquid chromatography (HPLC) were extensively used. Subsequently, it was attempted to biodegrade untreated and pretreated H-acid using activated sludge from the textile industry acclimatized to H-acid. It was found that photocatalytic pretreatment of H-acid for 30 min, during which period approximately 8-10% chemical oxygen demand (COD) removal occurred, can be coupled to second-stage biological treatment for achieving enhanced biodegradation of H-acid.

Influence of anode material on electrochemical oxidation for the treatment of tannery wastewater.

The treatment of tannery wastewater by electrochemical oxidation, mediated by an electro-generated species was carried out under galvanostatic conditions in an electrochemical reactor equipped with anodes based on noble metals and metal oxides (Ti/Pt-Ir, Ti/PbO2, Ti/PdO-Co3O4 and Ti/RhO(x)-TiO2). The decrease in time of chemical oxygen demand, nitrogen (TKN and ammonia), Cr and sulphides was monitored. The study showed that the rate of pollutant removal was significantly influenced by the type of anode material and electrochemical parameters. Different mechanisms contributed to the removal of pollutants when the reactor operated under conditions close to the limiting current for chlorine evolution and under much higher current density, with the reactor performing better at a high current/voltage. The kinetic pseudo-first order model applied for the interpretation of the results showed that the Ti/Pt-Ir and Ti/PdO-Co3O4 anodes performed better than the other two electrodes under the majority of tested conditions, with the highest rate of removal obtained for ammonia (kinetic rate constant k=0.75 min(-1)). Electrochemical oxidation can be applied as a post-treatment after the conventional biological process in order to remove the residual ammonia with low energy consumption (0.4 kWh m(-3)).

Heterogenous solar photocatalysis of two commercial reactive azo dyes.

Two commercial reactive azo dyes--Reactive Black 5 (RB5) and Reactive Orange 16 (RO 16) have been treated by titanium dioxide and Zinc oxide photocatalysts separately under presence of sunlight. It is observed that solar photocatalytic treatment is effective in terms of colour and COD. The photodegradation efficiency of zinc oxide is comparable with TiO2 at pH 5-6 for RO16. The extent of decolourization and degradation of RB5 is greater in presence of zinc oxide photocatalyst than TiO2 at pH 5- 6. Zinc oxide undergoes <1% photodissolution after 6 hours of solar irradiation at working pH.

Preliminary studies on bacterial decolorization of H-acid based azo dye-reactive black 5.

A co-culture acclimatized to H-acid was used to degrade Reactive Black 5 (RB 5), a bis azo dye having central H-acid function. The effect of substrate concentration, pH and medium composition on the decolorization has been investigated. Decolorization was found independent of pH. Luria-Bertani broth favored decolorization over Yeast Extract; however further decolorization experiments have been conducted using Yeast Extract. The Michaelis-Menten Kinetic model is found to describe the dependence of specific decolorization rate on the RB 5 dye concentration.

Rate enhancing effect of bromide on the removal of ammonia at Ti/PbO2 anode.

Electrochemical oxidation of ammonium (NH4+) at Ti/PbO2 anode in chloride-free and chloride containing aqueous solutions was studied. The experimental results have shown that oxidation of NH4- is ensured only in the presence of chloride. The oxidation of NH4+ is found to follow pseudo first-order kinetics. Bromide in the electrolyte is found to cause substantial rate enhancing effect on the ammonium removal. The dependence of k on the current density as well as halide concentration is also discussed in this study.

Bioremediation of soil contaminated with organic compounds with special reference to acrylonitrile.

Enrichment of acrylonitrile (AN) degrading bacterial culture from contaminated soil resulted in the isolation of two cultures which were identified as gram negative small rods (C1) and gram positive cocci (C2). One of the cultures (C1) was identified as Citrobacter fruendii on the basis of biochemical and physiological tests. Both the cultures (C1 and C2) were able to utilize acrylonitrile up to a concentration of 2000 mg/l as the sole source of carbon and nitrogen. The studies also confirmed that the acrylonitrile contaminated soil when ploughed with well mixed AN degrading culture, diammonium phosphate and farmyard manure, could be completely remediated within two months from the date of soil amendment.

Electrochemical treatment of wastewater from a phosphoric acid manufacturing plant.

Phosphoric acid plant wastewater containing fluoride, phosphate and chemical oxygen demand etc., was treated using electrooxidation and electroflocculation methods. A maximum of 82% F- and 22.7% COD were removed using Ti/Pt(5c) under electrooxidative conditions. Electrooxidation with respect to F- removal is found mass-transfer limited, and removals below 5-6 mg/L F- are not achievable. Electroflocculation using Al anode resulted in better removal of F-, COD and PO4(3-). The various results obtained are discussed in this paper.

Biohydrolysis of urea from urea-bearing wastewater.

Biological stabilization of urea is a two staged process; (i) urea hydrolysis and (ii) ammonia stripping/nitrification-denitrification. Ammonia thus produced is either stripped off by usual methods or after converting into nitrate using chemoautotrophic bacteria. On denitrification, nitrate is finally converted into nitrogen gas by means of heterotrophic bacteria. Details of stabilization of urea from urea bearing wastewater using urea biohydrolyser are presented in this paper.