Papers by Nilanjan Maitra
Soil and Sediment Contamination: An International Journal, 2017
ABSTRACT Biogeochemical reduction and mobilization of sediment-bound arsenic have triggered wides... more ABSTRACT Biogeochemical reduction and mobilization of sediment-bound arsenic have triggered widespread groundwater arsenic contamination and public health emergency in Bengal Delta. The present study examines arsenic reduction ability of pond sediment microbiota and their diversity from arsenic-affected villages. Arsenic reduction ability of pond sediment microbiota and individual bacterial isolates were studied in sediment microcosm and in culture medium. Arsenic-reducing strains were identified from 16S rDNA sequences. Pond sediment microflora caused profuse arsenic reduction under anoxic and partial anoxic conditions, and under the influence of labile organic matter. Prominent arsenic-reducing strains were identified as Chryseobacterium sp., Pseudomonas sp., Acinetobacter sp., and Comamonas aquatica. The presence of partial-to-true anoxic conditions, typical of pond ecosystems in this region and labile organic matter, as well as organic manure applications in ponds for aquaculture, strongly favored arsenic reduction by sediment microflora. The Bengal Delta plain is bestowed with thousands of aquaculture ponds and floodplain wetlands which might act as important sites for microbial reduction and mobilization of arsenic to the groundwater hydrologic system in the region.
Exploratory Animal and Medical Research, 2021
Soil and Sediment Contamination: An International Journal
ABSTRACT Biogeochemical reduction and mobilization of sediment-bound arsenic have triggered wides... more ABSTRACT Biogeochemical reduction and mobilization of sediment-bound arsenic have triggered widespread groundwater arsenic contamination and public health emergency in Bengal Delta. The present study examines arsenic reduction ability of pond sediment microbiota and their diversity from arsenic-affected villages. Arsenic reduction ability of pond sediment microbiota and individual bacterial isolates were studied in sediment microcosm and in culture medium. Arsenic-reducing strains were identified from 16S rDNA sequences. Pond sediment microflora caused profuse arsenic reduction under anoxic and partial anoxic conditions, and under the influence of labile organic matter. Prominent arsenic-reducing strains were identified as Chryseobacterium sp., Pseudomonas sp., Acinetobacter sp., and Comamonas aquatica. The presence of partial-to-true anoxic conditions, typical of pond ecosystems in this region and labile organic matter, as well as organic manure applications in ponds for aquaculture, strongly favored arsenic reduction by sediment microflora. The Bengal Delta plain is bestowed with thousands of aquaculture ponds and floodplain wetlands which might act as important sites for microbial reduction and mobilization of arsenic to the groundwater hydrologic system in the region.
Environmental Science and Pollution Research
Biogeochemical release of soil-bound arsenic (As) governs mobilization of the toxic metalloid int... more Biogeochemical release of soil-bound arsenic (As) governs mobilization of the toxic metalloid into the groundwater. The present study has examined AsV-reduction ability of bacteria from anoxic aquatic sediments that might contribute to arsenic mobilization in the Bengal Delta. Arsenic-reducing bacteria from deep layers of pond sediment were enriched and isolated in anaerobic environments and AsV reduction was assessed in culture medium. The pond sediment enrichments harboured AsV-reducing bacteria belonging to the phyla Firmicutes and Proteobacteria with dominance of Paraclostridium benzoelyticum and P. bifermentans. Among total 17 isolates, the respiratory reductase genes were not detected by the most common primers and only 3 strains had arsenic reductase ArsC gene suggesting involvement of resistance and some unknown mechanisms in AsV reduction. Presence of high levels of organic matter, As, and As-reducing bacteria might make deep aquatic sediments a hot spot of As mobilization and aquifer contamination.
Hydrobiologia, Feb 1, 2015
Phosphorus (P) is a limiting nutrient in some freshwater ecosystems. Phosphate solubilizing bacte... more Phosphorus (P) is a limiting nutrient in some freshwater ecosystems. Phosphate solubilizing bacteria (PSB) are candidates for enhancing P availability in rhizoplane, but their P release potential in freshwater environments needs further evaluations. This study conducted in floodplain wetlands correlated PSB abundance, decline in sediment pH, and natural mobilization of sediment CaP. PSB were abundantly present in floodplain wetland waters, sediments, and in river and ponds, showing low to moderate CaP solubilization activity; PSB from Churni River and Bhomra wetland sediments had comparatively higher activity than those from other environments. In laboratory sediment microcosms, PSB were effective in enhancing available P concentration in interstitial water indicating their P release potential. However, P-fractionation of incubated sediments showed only a short-term decline in CaP by PSB, suggesting that CaP might not be their sole or preferred metabolic target. Despite low to moderate activity in culture medium, high population density and efficacy in P release in sediment suggest significant role of PSB in P cycling in freshwater environments.
Geomicrobiology, 2015
Microbial mobilization of sediment calcium-bound P constitutes an important process of P cycling ... more Microbial mobilization of sediment calcium-bound P constitutes an important process of P cycling in aquatic environments. The present study was conducted to identify the bacterial community responsible for inorganic phosphate solubilization in tropical oxbow lakes. Fifty eight phosphate-solubilizing bacteria were isolated from bottom soil, water, and fish gut and examined for solubilization of tricalcium phosphate. Results revealed aquatic PSB to be low-to-moderately capable in P solubilization (mean: 33.5 mg P L−1; range: 6.3–68.8 mg P L−1), and bacteria from wetland sediment and water were more effective than those from fish gut. The PSB were identified to belong to diverse genera, viz. Bacillus, Brevibacillus, Enterobacter, Agrobacterium, Pseudomonas, Acinetobacter, Microbacterium, Curtobacterium, Stenotrophomonas and Novosphingobium. The findings help in understanding the microbial role in inorganic P solubilization and identifying important P solubilizers in freshwater environments.
A soil bacterium capable of utilizing pentachlorophenol (PEP) as a sole source of carbon and ener... more A soil bacterium capable of utilizing pentachlorophenol (PEP) as a sole source of carbon and energy was examined for its morphological, biochemical, cultural, and physiological characteristics. The organism was a member of the coryneform group of bacteria, probably in the genusArthrobacter. The isolate exhibited a doubling time of 4-5 h while growing on either glucose or PCP as the sole carbon source. The growth rate on PeP was essentially constant between 10-135 mg/1. At higher concentrations of PeP the growth rate was inhibited. The organism was found to be an excellent scavenger ofPCP; a Monod saturation constant of 1.12 mg/1 was obtained from chemostat measurements. In many cases conventional biological systems have been shown to be ineffective in treating PCP contaminated wastes (Jank and Fowlie 1980). Attempting to understand and improve these systems has been made difficult by the fact that there are essentially no studies in the literature on the kinetics of growth on PCP. Moreover, published information on the taxonomic characteristics of PeP-degrading bacteria is quite limited. This report describes the isolation and characterization of an axenic bacterial culture capable of utilizing PeP as a sole source of carbon and energy. The growth characteristics of the culture on Trypticase soy broth, PCP, and glucose and its degree of metabolism of PCP are elucidated.
Genome announcements, Jan 30, 2014
Bacillus sp. strain CPSM8 is an efficient solubilizer and mineralizer of phosphorus. Here, we pre... more Bacillus sp. strain CPSM8 is an efficient solubilizer and mineralizer of phosphorus. Here, we present the 4.39-Mb draft genome sequence of the strain, providing insight into the phosphorus-releasing genes related to productivity in aquatic habitats.
Aquatic Ecosystem Health & Management, 2015
Inorganic phosphorus is one of the critical nutrients determining trophic state and freshwater pr... more Inorganic phosphorus is one of the critical nutrients determining trophic state and freshwater productivity. Sediment may act as a sink or source of phosphorus to the overlying water depending on its pH, redox state, various forms of phosphorus present, etc. To examine potential sorption or mobilization of sediment phosphorus in floodplain wetlands, the amount and distribution of phosphorus fractions were evaluated using a sequential chemical extraction procedure. Exceedingly high levels of total phosphorus (mean: 6040 ± 344, 5470 ± 363 mg kg−1), consisting largely of organic and refractory fraction (70 – 98%), followed by calcium-phosphorus (mean: 584 ± 31.3, 143 ± 8.42 mg kg−1) and iron-phosphorus (mean: 108 ± 10.1, 91.0 ± 7.68 mg kg−1) were recorded respectively in Bhomra and Akaipur wetlands of West Bengal, India. The inorganic phosphorus, comprising the loosely sorbed phosphorus and all the mineral bound forms contributed only about 6–14% to the total phosphorus indicating thei...
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Papers by Nilanjan Maitra