Please use this identifier to cite or link to this item: http://krishikosh.egranth.ac.in/handle/1/5810022174
Authors: UMA, G. P.
Advisor: DR.PRABHURAJ A.
Title: CHARACTERIZATION OF EXTRACELLULAR SECRETION OF SYMBIOTIC BACTERIUM, Photorhabdus luminescens (THOMAS & POINAR)
Language: en
Type: Thesis
Agrotags: null
Abstract: Survey on EPN in ten Agro-climatic Zones of Karnataka yielded 15 Heterorhabitis spp., from 68 locations representing different habitat with highest recovery from sugarcane crop ecosystem (42%). The cultural characteristics of symbiotic bacteria isolated from Heterorhabitis spp. revealed that primary form of all isolates were circular to irregular, opaque to transparent with entire edge in beginning and undulating later. Further, isolates fall into three pigmentation group of brick/dark red color over laid by blue, pink to dark pink over laid by blue and greenish to brown color over laid by blue. All the isolates of P. luminescens are gram –ve, motile, catalase positive and bioluminescent. Biochemically, they are positive for MR test, citrate utilization, indole production and H2S production but negative for VP test and showed variability for gelatin liquification, casein hydrolysis, urease, phenyldeaminase, decarboxylase, CHO assimilation and antibiotic susceptibility tests. Phenotypic clustering yielded five groups with similarity co-efficient of 32-83 per cent. Further, P. luminescens isolates with 1500 bp length showed 16S rRNA gene sequence with 81- 93 per cent similarity. Pathogenicity tests confirmed that among 15 isolates KZ6S1 isolate was more pathogenic to all three insects tested viz.,Tetranychus macferlaei; Phenococcus solenopsis and Plutella xylostella with 100, 88.33 and 40 per cent mortality, respectively. The k-means clustering based on the virility on all the three insects revealed KZ6S1 was the most virulent isolate. Qualitative and quantitative estimation of extracellular secretions revealed peak chitinase enzyme activity at log phase (12-24 h), peak protease activity at stationary phase (24-48 h) and peak lipase activity at late stationary phase (48-72 h). Further, SDS-PAGE gel electrophoresis yielded different molecular weight protein. However, in most virulent isolates 43.9 kDa protein was common. In conclusion, the virility of P. luminescens isolates was attributed to protease activity and chitinase and lipase enzymes only support the process of cell lysis and degradation.
Subject: Agricultural Entomology
Theme: CHARACTERIZATION OF EXTRACELLULAR SECRETION OF SYMBIOTIC BACTERIUM, Photorhabdus luminescens (THOMAS & POINAR)
These Type: Ph.D
Issue Date: 2015-06-30
Appears in Collections:Thesis

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