N Qamar1, Y Rehman2, S Hasnain1,2. 1. School of Biological Sciences, University of the Punjab, Lahore, Pakistan. 2. Department of Microbiology and Molecular Genetics, University of the Punjab, Lahore, Pakistan.
Abstract
AIMS: The aim of the study was to explore irrigation water polluted with industrial waste and corresponding cropland to screen bacteria for As detoxification and plant growth promotion. METHODS AND RESULTS: Plant growth-promoting (PGP) As-resistant cropland bacteria were isolated from contaminated irrigation water and corresponding agricultural soil. Phylogenetic analysis revealed that the isolates belonged to two distinct bacterial lineages; Firmicutes and γ-Proteobacteria. Maximum As(V) resistance was exhibited by Klebsiella pneumoniae T22 and Klebsiella oxytoca N53 (550 mmol l-1 ), whereas maximum resistance against As(III) was exhibited by K. oxytoca N53 (200 mmol l-1 ). Maximum As(V) reduction was shown by K. pneumoniae T22 (6·7 mmol l-1 ), whereas maximum As(III) oxidation was exhibited by Bacillus subtilis T23 (4·8 mmol l-1 ). As resistance genes arsB and ACR3 were detected in many of the isolates through polymerase chain reaction. Many of these isolates exhibited PGP traits such as hydrogen cyanide and auxin production as well as phosphate solubilization. The bacterial strains were able to enhance Triticum aestivum growth both in the absence and presence of As, and statistically significant increase in shoot and root lengths was observed especially in case of Acinetobacter lwoffii T24 and Citrobacter freundii N52-treated plants. CONCLUSIONS: Cropland bacteria have the ability to support plant growth. Bacteria of croplands irrigated with industrially polluted water develop resistance against toxicants. These bacteria are helpful for the plant growth in such contaminated lands. SIGNIFICANCE AND IMPACT OF THE STUDY: The bacteria capable of both As detoxification and plant growth promotion, such as A. lwoffii T24 and C. freundii N52, are ideal for remediation and reclamation of polluted lands for agriculture purposes.
AIMS: The aim of the study was to explore irrigation water polluted with industrial waste and corresponding cropland to screen bacteria for As detoxification and plant growth promotion. METHODS AND RESULTS: Plant growth-promoting (PGP) As-resistant cropland bacteria were isolated from contaminated irrigation water and corresponding agricultural soil. Phylogenetic analysis revealed that the isolates belonged to two distinct bacterial lineages; Firmicutes and γ-Proteobacteria. Maximum As(V) resistance was exhibited by Klebsiella pneumoniae T22 and Klebsiella oxytoca N53 (550 mmol l-1 ), whereas maximum resistance against As(III) was exhibited by K. oxytoca N53 (200 mmol l-1 ). Maximum As(V) reduction was shown by K. pneumoniae T22 (6·7 mmol l-1 ), whereas maximum As(III) oxidation was exhibited by Bacillus subtilis T23 (4·8 mmol l-1 ). As resistance genes arsB and ACR3 were detected in many of the isolates through polymerase chain reaction. Many of these isolates exhibited PGP traits such ashydrogen cyanide and auxin production as well asphosphate solubilization. The bacterial strains were able to enhance Triticum aestivum growth both in the absence and presence of As, and statistically significant increase in shoot and root lengths was observed especially in case of Acinetobacter lwoffii T24 and Citrobacter freundii N52-treated plants. CONCLUSIONS: Cropland bacteria have the ability to support plant growth. Bacteria of croplands irrigated with industrially polluted water develop resistance against toxicants. These bacteria are helpful for the plant growth in such contaminated lands. SIGNIFICANCE AND IMPACT OF THE STUDY: The bacteria capable of both As detoxification and plant growth promotion, such asA. lwoffii T24 and C. freundii N52, are ideal for remediation and reclamation of polluted lands for agriculture purposes.