Sulphur oxidising bacteria in mangrove ecosystem: A review

Mangrove soils are anoxic, sulphidic and variable since their chemistry is regulated by a variety of factors such as texture, tidal range and elevation, redox state, bioturbation intensity, forest type, temperature and rainfall. Sulphur-oxidizing bacteria such as photoautotrophs, chemolithotrophs and heterotrophs play an important role in the mangrove environment for the oxidation of the toxic sulphide produced by sulphur reducing bacteria and act as a key driving force behind all sulphur transformations in the mangrove ecosystem which is most essential to maintain the sulphur cycle as well as eco health. These overviews summarizes the current state of knowledge of diversity and important biotechnological contributions of these microorganisms in agriculture, bio fertility, reduction of environmental pollution, maintenance of the productivity of ecosystems and also highlight areas in which further research is needed to increase our basic understanding of physiology, genomics and proteomics of these microorganisms which is most essential. Keywords: Mangrove habitat, sulphur oxidising bacteria, sulphur cycle, sulphide oxidase.African Journal of Biotechnology Vol 13(29) 2897-290

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Characterization and evaluation of stress and heavy metal tolerance of some predominant Gram negative halotolerant bacteria from mangrove soils of Bhitarkanika, Orissa, India

In the present study both Gram positive and Gram negative bacteria were isolated using enrichment media from five different stations from mangroves soils of Bhitarkanika, Orissa, India. Among the bacterial populations studied, the Gram negative bacterial population was found to be more in all the stations. Out of several Gram negative bacterial isolates, six predominant and morphologically distinct isolates were selected and characterized. Phenotypical the isolates were identified as one each of Pseudomonas aeruginosa and P. alcaligenes and two strains each of Methylococcus sp. and Desulfotomaculum sp. The strain P. aeruginosa and one strain of Methylococcus sp. tolerated up to13% NaCl and 10% sea salt, respectively. But the other four isolates tolerated 10% NaCl as well as sea salt. Most of the organisms were sensitive to several antibiotics tested except for the antifungalantibiotic Nystatin. The stress tolerant enzyme activities for catalase, peroxidase, polyphenol oxidase, ascorbate peroxidase, ascorbic acid oxidase were found to be variable among the strains. Evaluation ofheavy metal tolerance towards the heavy metals; ZnSO4, CuSO4, NiCl2, CdNO3 and K2CrO4 showed that the isolates tolerated 600 - 1000 ppm K2CrO4 but only up to 10 - 20 ppm CdNO3

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Antimicrobial activity of Diospyros melanoxylon bark from Similipal Biosphere Reserve, Orissa, India

The antimicrobial activity of five extracts of Diospyros melanoxylon Roxb. bark collected from Similipal Biosphere Reserve, Orissa was evaluated against human pathogenic bacteria and fungi. The extractsincluding both polar and non polar solvents; petroleum ether, chloroform, ethanol, methanol and aqueous were evaluated for their antimicrobial activity against three gram positive and five gramnegative bacteria as well as three fungal strains. Although, all the five extracts exhibited promising antibacterial activities, yet maximum activity was observed in ethanol extract. In case of antifungalactivity, except petroleum ether extract none of the extracts were found to be active against the fungal strains. MIC values for most of the extracts ranged from 1.5 to 6 mg/ml, while MBC values varied from 3mg/ml to values greater than 12 mg/ml. Phytochemical analysis exhibited the presence of steroids, alkaloids, glycoside, proteins, tannins, phenolic compounds, carbohydrates, gums and mucilage inacetone, methanol and ethanol extracts with maximum phytochemicals in ethanol extract. Least phytochemicals was observed in case of petroleum ether. These results, so obtained, demonstrate thebroad spectrum activity of D. melanoxylon bark extracts which may be useful in treatment of various microbial infections. However, the active components responsible for antimicrobial activity need to beevaluated

Impact of heavy metals on bacterial communities from mangrove soils of the Mahanadi Delta (India)

This study aimed to assess soil nutrient status and heavy metal content and their impact on the predominant soil bacterial communities of mangroves of the Mahanadi Delta. Mangrove soil of the Mahanadi Delta is slightly acidic and the levels of soil nutrients such as carbon, nitrogen, phosphorous and potash vary with season and site. The seasonal average concentrations (g/g) of various heavy metals were in the range: 14810-63370 (Fe), 2.8-32.6 (Cu), 13.4-55.7 (Ni), 1.8-7.9 (Cd), 16.6-54.7 (Pb), 24.4-132.5 (Zn) and 13.3-48.2 (Co). Among the different heavy metals analysed, Co, Cu and Cd were above their permissible limits, as prescribed by Indian Standards (Co=17g/g, Cu=30 g/g, Cd=3-6 g/g), indicating pollution in the mangrove soil. A viable plate count revealed the presence of different groups of bacteria in the mangrove soil, i.e. heterotrophs, free-living N-2 fixers, nitrifyers, denitrifyers, phosphate solubilisers, cellulose degraders and sulfur oxidisers. Principal component analysis performed using multivariate statistical methods showed a positive relationship between soil nutrients and microbial load. Whereas metal content such as Cu, Co and Ni showed a negative impact on some of the studied soil bacteria