Beneficial plant-associated bacteria play a key role in supporting and/or promoting plant growth and health. Plant growth promoting bacteria present in the rhizosphere of crop plants can directly affect plant metabolism or modulate phytohormone production or degradation. We isolated 355 bacteria from the rhizosphere of rice plants grown in the farmers' fields in the coastal rice field soil from five different locations of the Ganjam district of Odisha, India. Six bacteria producing both ACC deaminase (ranging from 603.94 to 1350.02 nmol α-ketobutyrate mg(-1) h(-1) ) and indole acetic acid (IAA; ranging from 10.54 to 37.65 μM ml(-1) ) in pure cultures were further identified using polyphasic taxonomy including BIOLOG((R)) , FAME analysis and the 16S rRNA gene sequencing. Phylogenetic analyses of the isolates resulted into five major clusters to include members of the genera Bacillus, Microbacterium, Methylophaga, Agromyces, and Paenibacillus. Seed inoculation of rice (cv. Naveen) by the six individual PGPR isolates had a considerable impact on different growth parameters including root elongation that was positively correlated with ACC deaminase activity and IAA production. The cultures also had other plant growth attributes including ammonia production and at least two isolates produced siderophores. Study indicates that presence of diverse rhizobacteria with effective growth-promoting traits, in the rice rhizosphere, may be exploited for a sustainable crop management under field conditions.
Submergence stress slows seed germination, imposes fatalities, and delays seedling establishment in rice. Seeds of submergence susceptible rice variety IR 42 were inoculated with four 1-aminocyclopropane-1-carboxylic acid (ACC) utilizing isolates viz., Bacillus sp. (AR-ACC1), Microbacterium sp. (AR-ACC2), Methylophaga sp. (AR-ACC3), and Paenibacillus sp. (ANR-ACC3) and subjected to submergence stress under controlled conditions for 7 days. Seeds treated with Microbacterium sp. AR-ACC2, Paenibacillus sp. ANR-ACC3, and Methylophaga sp. AR-ACC3 significantly enhanced the germination percentage (GP), seedling vigor index (SVI), and other growth parameters like root and shoot length and total chlorophyll contents, when compared with nonbacterized seeds submerged similarly. However, the values were statistically at par when control seeds were treated with l-α-(2-aminoethoxyvinyl) glycine hydrochloride (AVG), a known inhibitor of ethylene production. Results suggest that stress ethylene production was significantly reduced by around 85% in seedlings treated with Microbacterium sp. AR-ACC2 as compared with untreated control seeds under submergence. Paenibacillus sp. ANR-ACC3 and Methylophaga sp. AR-ACC3 were the next effective strains. Ethylene synthesis in seedlings was statistically at par with seeds treated with AVG suggesting ACC deaminase can effectively reduce ethylene levels in plants subjected to submergence. Bacillus sp. (AR-ACC1) was neither able to significantly promote seedling growth parameters nor inhibit ethylene production as compared with control seeds. Results suggest that flooded soil planted to rice harbor microorganisms with plant growth-promoting properties that can be used effectively to alleviate submergence stresses in susceptible rice varieties under field conditions.
Background. Xpert-MTB/RIF assay or Cartridge-Based Nucleic Acid Amplification Test (CBNAAT) helps in rapid diagnosis of tuberculosis (TB).Methods. Specific samples were collected and carried to Regional Medical Research Centre where these were taken up for CBNAAT and culture in Lowenstein-Jensen media. Appropriate samples were sent to the Designated Microscopy Centre (DMC) of our institute for acid-fast bacilli (AFB) smear examination. Diagnostic measures, such as sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy of Xpert-MTB/RIF were reported considering mycobacterial culture and a composite reference standard (CRS) as Gold standard.Results. We studied 335 samples. Lymph node fine needle aspirate was the most common sample (32.5%) followed by pleural fluid (29.3%). The overall sensitivity and specificity of Xpert-MTB/RIF was determined to be 26.5% (95% CI [confidence interval] 20.8-32.8) and 100% (95% CI 96.8-100), respectively. The sensitivity and specificity of CBNAAT in relation to mycobacterial culture, however, was 78.8% (95% CI 61.1-91.0) and 89.1% (95% CI 85-92.4), respectively. Both were highest for pus, cerebrospinal fluid and lymph node fine needle aspirate samples.Conclusions. Xpert-MTB/RIF may be useful for samples, like cold abscess and lymph node fine needle aspirate or biopsy specimens. However, its routine use in case of serosal fluids is not recommended because of its lower sensitivity.
Statistical AnalysisThe data were entered in Microsoft Excel spread-sheet. Comparison of means was done using Fischer's exact 't' test (with sample size less than 40) or quantify agreement with Kappa value (sample size more than 40). The Kappa value <0.4 was considered as poor agreement
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