Department of Biological Sciences

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Subject: search.filters.subject.Pseudomonas aeruginosa

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    Endophytic Bacteria Pseudomonas aeruginosa PM389 Subsists Host’s (Triticum aestivum) Immune Response for Gaining Entry Inside the Host
    (JPAM, 2021) Jha, Prabhat Nath
    The present study was designed to compare the defense response of the host plant towards endophytic bacteria Pseudomonas aeruginosa PM389 and pathogenic bacteria Erwinia carotovora and to correlate the level of defense enzymes vis-a-vis bacterial colonization in the host. Wheat seedlings were treated with 107-108 cells ml-1 endophytic and pathogenic bacteria in the separate experimental set-up, and the level of plant defense enzyme was measured at various time intervals. Comparatively reduced level of most defense enzymes was produced in endophytic bacteria treated plants. While the endophytic bacterial population was almost constant after 24 HAI (hour after inoculation), the population of pathogenic bacteria kept fluctuating during the study period from 24 HAI. Unlike pathogenic bacteria, we observed attenuated defense response in challenged host plants towards endophytic bacteria, which helps endophytes establish inside plant. This study would be useful for understanding the mechanism of colonization and strategies of endophytes to fight against the host defense response.
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    Exploring Functional Diversity and Community Structure of Diazotrophic Endophytic Bacteria Associated with Pennisetum glaucum Growing under Field in a Semi-Arid Region
    (MDPI, 2022-06) Jha, Prabhat Nath
    Diazotrophic endophytic bacteria (DEB) are the key drivers of nitrogen fixation in rainfed soil ecosystems and, hence, can influence the growth and yield of crop plants. Therefore, the present work investigated the structure and composition of the DEB community at different growth stages of field-grown pearl millet plants, employing the cultivation-dependent method. Diazotrophy of the bacterial isolates was confirmed by acetylene reduction assay and amplification of the nifH gene. ERIC-PCR-based DNA fingerprinting, followed by 16S rRNA gene analysis of isolates recovered at different time intervals, demonstrated the highest bacterial diversity during early (up to 28 DAS (Days after sowing)) and late (63 DAS onwards) stages, as compared to the vegetative growth stage (28–56 DAS). Among all species, Pseudomonas aeruginosa was the most dominant endophyte. Assuming modulation of the immune response as one of the tactics for successful colonization of P. aeruginosa PM389, we studied the expression of the profile of defense genes of wheat, used as a host plant, in response to P. aeruginosa inoculation. Most of the pathogenesis-related PR genes were induced initially (at 6 h after infection (HAI)), followed by their downregulation at 12 HAI. The trend of bacterial colonization was quantified by qPCR of 16S rRNAs. The results obtained in the present study indicated an attenuated defense response in host plants towards endophytic bacteria, which is an important feature that helps endophytes establish themselves inside the endosphere of roots.
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    Purification and characterization of a solvent stable aminopeptidase from Pseudomonas aeruginosa: Cloning and analysis of aminopeptidase gene conferring solvent stability
    (Elsiever, 2010-05-05) Sharma, Rita
    Aminopeptidase from a solvent tolerant strain Pseudomonas aeruginosa PseA was purified and studied for its biochemical and molecular characteristics. Ion-exchange chromatography resulted in 11.9-fold purification and 38% recovery of the 56 kDa enzyme. The enzyme was found to be stable over a pH range of 6.0–8.0 and appreciably thermostable up to 70 °C. PseA aminopeptidase exhibited Km of 3.02 mM and Vmax of 6.71 μmol/mg/min towards l-Leu-p-nitroanilide. Remarkable stability in both hydrophilic and hydrophobic solvents makes PseA aminopeptidase unique. Partial N-terminal sequence of enzyme showed exact match with probable aminopeptidase of P. aeruginosa PAO1, coded by gene pepB. Polymerase chain reaction amplified the 1611-bp open reading frame encoding a 57.51 kDa, 536 amino acid PseA PepB polypeptide. The deduced PseA PepB protein sequence contained a 24-residue signal peptide (2.57 kDa) followed by a 1.28 kDa propeptide and a mature product of 500 residues. Search for conserved domain in PseA aminopeptidase explored its place in zinc-metallopeptidase family. Primary sequence analysis showed the hydrophobic inclination of the protein; and the 3D structure modeling elucidated the presence of a high content of hydrophobic residues on its surface probably imparting solvent stability to it. The enzyme might find potential applications in non-aqueous enzymology due to its marked thermostability and striking solvent stability.
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    Natural occurrence of Pseudomonas aeruginosa, a dominant cultivable diazotrophic endophytic bacterium colonizing Pennisetum glaucum (L.) R. Br.
    (Elsiever, 2013) Jha, Prabhat N.; Panwar, Jitendra
    Endophytic microbial communities can have strong influence on the growth of their host plants. The present study reports a diazotrophic endophytic bacterial species that colonizes predominantly Pennisetum glaucum (pearl millet) and remains stabilized throughout the latter's various growth stages under field conditions. Qualitative and quantitative changes in the endophytic bacterial population structure were examined during the plant growth period at regular intervals of 7 days up to harvesting. DNA fingerprinting (ERIC-PCR) was used as a biomarker to track the identity of various isolates obtained at different time intervals. Identification of representative bacterial species corresponding to different ERIC types was made on the basis of 16S rRNA gene sequence analysis. Based on the colony forming unit (cfu) count of bacterial isolates observed at various growth stages, Pseudomonas aeruginosa PM389 was found to be the dominant diazotrophic species among the cultivable endophytes colonizing pearl millet. The population of P. aeruginosa was detected in the host 21 days after sowing (DAS), indicating its entry in plant roots from soil and suggesting its non-vertical transfer in pearl millet. Moreover, an upward migration of this dominant diazotrophic bacterial species to shoots was observed with the plant growth. Further evaluation of P. aeruginosa PM389 revealed its various plant growth promoting properties viz. nitrogen fixation, mineral phosphate solubilization, siderophore production and antagonistic properties.