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Isolation of Arsenic Oxidizing-reducing Bacteria and Reclamation of as (iii) in Invitro Condition

Umme Aminun Naher
Senior Scientific Officer
Soil Science Division, BRRI Gazipur

S. M. Mofizul Islam
Scientific Officer
Soil Science Division, BRRI Gazipur

Abstract/ Executive Summary:

Soil and water background of total As at Bhanga was 13.3 mg/kg and 160 µg/l, respectively. The As-oxidizing bacterial population was found only in one soil sample while in all water samples both the species of bacteria were present. The population of As-reduction bacteria was higher compared to As-oxidation bacteria. A number of 36 As oxidizing-reducing bacteria were isolated and both the species tolerated 7 ppm of arsenic. Arsenic oxidizing bacteria were able to use As(III) for its metabolic activity and consequently decreased about 71-99% of As(III) in the broth supplemented with 7000 ppb of NaAsO₂after 7 days of incubation. Among the tested 10 oxidizers, strain 1 and 2 were found most efficient to use As(III) followed by strain 8. The verification of the transforming ability was carried out by using AgNO₃ method. Minimal salt agar plates with brownish precipitate revealed the presence of arsenate and activity of arsenite-oxidizing bacteria, while the presence of bright yellow precipitation was the activity of As-reducing bacteria.

Keywords: Arsenic, Arsenic oxidation-reduction bacteria, Detoxification.

Location: BRRI experimental farm, Gazipur

Start Date: 01-07-2009

End Date: 30-06-2010

Program Area: Crop-Soil-Water Management

Commodity: Arsenic

Objectives:

To isolate potential arsenic oxidation-reduction bacteria
To determine its capability for detoxification of As from

Methodology:

Arsenic oxidizing-reduction bacteria were isolated from arsenic contaminated soil and water samples of Bhanga, Faridpur. The isolation was done within seven days after sample collection. Exactly one gram of soil sample were taken into 95 ml sterile distil water and a series of 10 fold dilution were prepared up to 10-8. About 0.1 ml of dilution was spread on each media plate. For water sample 1 ml of sample was added into 99 ml sterile distil water. As oxidizing-reducing bacterial populations was determined using spread plate count method in minimal salt (MS) medium. The minimum salt medium was supplemented separately with 7 ppm of sodium arsenite (NaAsO₂) for isolation of As-oxidizing and 7 ppm of sodium arsenate (Na₂HAsO₄) for As-reduction bacteria. After 3 days of incubation population were counted. Verification of the transforming ability of the isolate was carried out by using of AgNO₃ method. The oxidation activity of the bacteria as well as reclamation of As (III) was determined from NaAsO₂ supplemented broth. Exactly, 7000 ppb of NaAsO₂was added to 50 ml of minimal salt broth. After 7 days of incubation the As (III) was determined using atomic absorption spectrophotometer with flow-injection hydride generation system.

Source of Information: Proceedings of BRRI Annual Internal Review for 2009- 2010

Article Link (Online Journal):

Funding Source:

1. Government

Budget:

Total Budget (Tk.) :

Achievement/Findings:

A number of 36 arsenic oxidation-reduction bacteria were isolated from Bhanga soil and water sample which can tolerate 7 ppm arsenic, either NaAsO₂ or Na₂HAsO₄. In invitro condition As-oxidizers were able to reduce 71-99% of As(III) in the broth supplemented with 7000 ppb of NaAsO₂ after 7 days of incubation.

Knowledge Management: Report/Proceedings