Prospecting Sulfur oxidizing bacteria from different eco-niches for their role in S mobilization for plant uptake
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Date
2020
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DIVISION OF MICROBIOLOGY INDIAN AGRICULTURAL RESEARCH INSTITUTE NEW DELHI-
Abstract
To push forward the frontiers of knowledge sulfur oxidizing bacteria (SOB) were
investigated in the present study because of their crucial role in the oxidation process
of unavailable form of sulfur in soil, bringing down the pH of soil making tied nutrients
available and influencing plant growth in sulfur deficient soil. SOBs were isolated,
characterized morpho-physiologically and genetically for identification of isolates.
Potential SOBs showing multi plant growth promoting (PGP) characteristics were
assessed in pot experimental trial with mustard as test crop in three types of soils
varying in S content.
In this study one twenty seven (127) putative sulfur oxidizing bacteria (SOB)
were isolated from different samples of rhizosphere soil of different crops, compost and
waste water through enrichment in Starkey broth. Out of 127 isolates 17 SOBs were
selected based on their ability to change the colour of Thiosulphate media (ThA) from
purple to yellow. Among the 17 SOBs best in vitro sulphate producers were
M3>M1>WC2 at 5 and 10 days and M3>WC2>M1 at 10-15 days of incubation
interval. SOB isolates were morphologically characterized and screened for stress
tolerance to different temperature, pH, salt and moisture content. Most of the SOBs
were able to grow over a wide range of pH of 6 to 10, at 350C and at 5%PEG. Other
than these conditions, few SOBs only could grow. The SOBs were also tested for PGP
activities like solubilization of P, K, ZnO, ZnCO3, CaCO3, N2 fixation, production of
IAA, HCN and siderophores. Out of 17 isolates M3 and WC2 isolates were positive in
maximum PGP activities along with sulphate production. 17 SOBs were genetically
characterized and identified as 3 genera of Thiobacillus, Bacillus, Klebsiella falling
under 2 phylum Firmicutes & Proteobacteria, and three classes viz., Bacilli,
Gammaproteobacteria and Betaproteobacteria respectively. Six potential SOBs
(Thiobacillus sajanensis-M3, Thiobacillus thioparus-WC2, Thiobacillus denitrificansG2, Klebsiella spp.-R1, Thiobacillus spp-CS1, Bacillus altitudinis-S3) were selected
for conducting the pot experiment with mustard as test crop with and without addition
of elemental sulfur to three types of soil and determined plant growth & soil parameters
at 60 DAS. The growth of plants were best in HS+S, MS+S, LS+S soil with the
inoculation of SOBs Thiobacillus sajanensis followed by T. thioparus clearly indicated
the role of SOBs in transformations of S in soil improving the uptake of sulphate by the
plants and influencing plant growth.
Description
T-10414