Tarun Kumar Mahto

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004915256760420

University of Delhi

Martin Luther University Halle-Wittenberg, Germany

Institute of Biology/Microbiology, Germany

3 years

Title- Factors affecting optimal growth of Xanthomonas campesteris pv. vesicatoria in plant apoplast. During BRAVE project I was involved in a research topic entitled ''factors influencing the optimal growth of Xanthomonas campestris pv. vesicatoria in pepper plant. Based on previous studies it was concluded that Citrate may be a probable substrate for bacterial growth in plant apoplast. Therefore, two citrate transporters cit and citH encoded by Xcv were deleted in order to observe their effect on bacterial growth and thus cit, cit H and cit-cit H double mutants were mutant were obtained. The growth analysis (in vitro) of the citrate transporters  cit, citH and a cit-citH double mutant  with MA minimal media and MA minimal media containing only Sucrose  shows no significant  difference in bacterial growth but with  MA minimal media  containing only citrate, the growth  of  citH and a cit-citH double mutant was compromised but not of  cit mutant. These data indicate that citrate is indeed an important factor for bacterial growth. Analysis of these mutants in planta and with apoplastic fluid extraction showed no significant difference in growth pattern with respect to WT. Because plant apoplast is very rich nutrient content these mutants are efficient enough to use other simple forms of nutrient available and they became dependent on citrate only when these simple forms of nutrient are restricted. Earlier studies on citrate transporters of Xanthomonas species also suggests that they play an important role in EPS (Exopolysaccharides)  and biofilm formation which is very crucial for bacterial growth and survival. My study on that aspect with these mutants revealed that deletion of these citrate transporter genes negatively affected the EPS production on these mutant with respect to the with type strain. Also, because EPS contribute to biofilm formation,  further investigation revealed that deletion of these genes affects negatively to biofilm formation. On the second part of my project, I was involved in understanding iron homeostasis in Xcv. To study this I was involved in the functional analysis of an iron uptake regulator gene(fur). Many attempts were made to knock down this iron uptake regulator gene but it was not completely deleted and at every attempt Xcv somehow is able to restore this gene which indicates that fur is a very crucial gene for Xcv survival and always finds a way to skip homologous recombination and thus it is able to save crucial gene for their survival . In order to further investigate the survival strategy of Xcv in iron-limiting condition, another gene called Zinc uptake regulator (Zur) of the same family was investigated by making a deletion mutant of Zur. The study revealed that they exhibit diauxic growth pattern in minimal media whereas with other carbon sources like citrate, sucrose and casaminoacid it showed a better growth than the wild-type strain. A Growth analysis in an iron limiting condition i.e in presence of iron chelators revealed that Xcv can grow in very high iron limiting conditions as the growth was only restricted when the concentration of iron chelator was very high (300µm).

1. Attended and presented poster and talks at regular meeting and workshops of SFB 648 ' Communication in Plants and their Response to the enviroment' including internation meeting (2014-2016) 

2. Attended and presented posters at ((VAAM) Annual Conference of the associtaion for General and applied Microbiology (2015-2017).