Molecular and eco-physiological characterization of arsenic (As)-transforming Achromobacter sp. KAs 3–5ᵀ from As-contaminated groundwater of West Bengal, India
2018
Mohapatra, Balaram | Satyanarayana, T. | Sar, Pinaki
Molecular and eco-physiological characterization of arsenic (As)-transforming and hydrocarbon-utilizing Achromobacter type strain KAs 3–5ᵀ has been investigated in order to gain an insight into As-geomicrobiology in the contaminated groundwater. The bacterium is isolated from As-rich groundwater of West Bengal, India. Comparative 16S rRNA gene sequence phylogenetic analysis confirmed that the strain KAs 3–5ᵀ is closely related to Achromobacter mucicolens LMG 26685ᵀ (99.17%) and Achromobacter animicus LMG 26690ᵀ (99.17%), thus affiliated to the genus Achromobacter. Strain KAs 3–5ᵀ is nonflagellated, mesophilic, facultative anaerobe, having a broad metabolic repertoire of using various sugars, sugar-/fatty acids, hydrocarbons as principal carbon substrates, and O₂, NO₃⁻, NO₂⁻, and Fe³⁺ as terminal electron acceptors. Growth with hydrocarbons led to cellular aggregation and adherence of the cells to the hydrocarbon particles confirmed through electron microscopic observations. The strain KAs 3–5ᵀ showed high As resistance (MIC of 5 mM for As³⁺, 25 mM for As⁵⁺) and reductive transformation of As⁵⁺ under aerobic conditions while utilizing both sugars and hydrocarbons. Molecular taxonomy specified a high genomic GC content (65.5 mol %), ubiquinone 8 (UQ-8) as respiratory quinone, spermidine as predominant polyamine in the bacterium. The differential presence of C₁₂:₀, C₁₄:₀ 2-OH, C₁₈:₁ ω7c, and C ₁₄:₀ iso 3-OH/ C₁₆:₁ iso fatty acids, phosphatidylglycerol (PG), phosphatidylcholine (PC), two unknown phospholipid (PL1, PL2) as polar lipids, low DNA-DNA relatedness (33.0–41.0%) with the Achromobacter members, and unique metabolic capacities clearly indicated the distinct genomic and physiological properties of strain KAs 3–5ᵀ among known species of the genus Achromobacter. These findings lead to improve our understanding on metabolic flexibility of bacteria residing in As-contaminated groundwater and As–bacteria interactions within oligotrophic aquifer system.
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