Microbiology


https://sites.google.com/a/gauhati.ac.in/research/#ds11092019 Endophytes and plant growth in tomato

https://sites.google.com/a/gauhati.ac.in/research/micro/#nb03092018 Glutamate metabolism in mycobacteria

Endophytes can prevent bacterial wilt disease and promote growth in tomato
Niraj Agarwala and coworkers show how a bacterium isolated from an indigenous plant can help tomato plant growth and prevent infections. This work is reported in Microbiological Research.


Authors
Heena Agarwal, Bhaskar Dowarah, Pooja Moni Baruah, Kuntala Sarma Bordoloi, Debasish B Krishnatreya, and Niraj Agarwala

Abstract
Endophytes are beneficial plant microbes which help the plants by producing various plant growth promoting substances and also by acting as biocontrol agents against various plant pathogens. In the present study, evaluation of endophytic bacteria isolated from Gnetum gnemon, an ethnomedicinal plant was carried out for their plant growth promoting (PGP) activity and antagonistic potential against bacterial wilt pathogen Ralstonia solanacearum. Initially a total of 40 endophytic bacteria were isolated which were clustered into 13 groups based on RFLP and BOX-PCR fingerprinting. These 13 representative isolates belonged to different genera of Bacillus (9), Solibacillus (1), Staphylococcus (2) and Caballeronia (1). Among them, six isolates were positive for production of IAA, the value of which ranged from 11.16 to 27.63 μg mL−1. Phosphate solubilisation in the range of 106.4 to –212.7 μg mL−1 was shown by three isolates. Eight isolates produced ammonia, the value of which ranged from 1.3 to 6.1 μmol mL−1. All tested isolates were positive for siderophore production. For extracellular enzyme production, 7 isolates were positive for protease, 8 for cellulase and 10 for amylase production. The isolates were also tested for their antagonistic activity against R. solanacearum in vitro and in planta assay using tomato seedlings. Staphylococcus warneri GL1 showed the highest biocontrol efficacy of 77.67% followed by Bacillus velezensis GL3 i.e. 70.1%. R. solanacearum antagonistic isolates were analysed for the presence of antimicrobial peptide biosynthesis genes bmyB, srfAA, fenD and ituC. All the antagonistic isolates showed the presence of all four genes, except the isolate Bacillus velezensis GMC2, where the gene for fengycin synthetase (fenD) was absent. Based on in vitro PGP traits, three isolates Bacillus velezensis GL3, Bacillus atrophaeus GMC1 and Bacillus megaterium GS2 were selected, these three endophytic bacteria individually and their consortia were tested for in planta PGP activities in tomato plants. Application of Bacillus velezensis GL3 alone and consortia of three isolates showed significant improvement in growth parameters such as shoot length, fresh weight and dry weight in a pot experiment. Colonisation of endosphere of treated tomato seedlings by the endophytic isolate Bacillus velezensis GL3 was confirmed by visualisation of colony morphology and BOX-PCR fingerprinting. Our study highlights the potential of endophytes associated with unexplored plants like G. gnemon for development of bioformulation aimed at enhancing plant growth and bacterial wilt disease control.

Botany    https://sites.google.com/a/gauhati.ac.in/research/#top 
 



Glutamate metabolism in mycobacteria

Nabanita Bhattacharyya and her fellow researchers show a way to control the glutamate metabolism in tuberculosis (TB) mycobacteria, which may prove to be a possible mechanism in controlling drug-resistant TB. This work is published in the journal mBio.




Authors
Nabanita Bhattacharyya, Irene Nailain Nkumama1, Zaccheus Newland-Smith1, Li-Ying Lin, Wen Yin
1
, Rebecca E Cullen
1
, Jack S Griffiths
1
, Alexander R Jarvis
1
, Michael J Price
1
, Pei Ying Chong
1
, Russell Wallis
1
, and Helen M O’Hare
1
1 from other institutions

Abstract
Tuberculosis (TB) is responsible for the death of almost 5,000 people every day, and the increasing prevalence of multidrug-resistant TB in the present world has become a matter of utmost concern. The mechanism by which the causal organism of TB Mycobacterium tuberculosis senses and responds to environmental stimuli have proven to be attractive targets for drug development. Recently, the TB research group of Dr. Helen M. O’Hare, in the Department of Infection Immunity and Inflammation (University of Leicester) showed that nutrients stimulate phosphorylation of protein GarA, which is a substrate of the protein kinase G (PknG) in Mycobacterium smegmatis and Mycobacterium tuberculosis and that the phosphorylation status of GarA regulates the central metabolism. In this investigation, we have presented the mechanism by which nutrients activate PknG. Two unknown genes are identified as co-conserved and co-expressed with PknG, whose products are a putative lipoprotein, GlnH, and putative transmembrane protein, GlnX. By using a genetic approach, the authors show that the membrane protein GlnX is functionally linked to PknG. They also propose that the amino acid concentration in the periplasm is sensed by GlnH and that protein-protein interaction allows transmission of this information across the membrane via GlnX to activate PknG.

Journal Reference
https://sites.google.com/a/gauhati.ac.in/research/micro/#top