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The world of halophilic bacteria is quite diverse. We fi nd representatives of three domains of life, archaea, bacteria and eukarya that are adapted to salt concentration upto saturation. The micro-organisms able to grow upto NaCl concentration (>300 g/l) are found all over the small subunit rRNA based tree of life. Their metabolic diversity is high as well encompassing oxygenic and anoxygenic phototrophs, aerobic heterotrophs, denitrifi ers, sulfate reducers, fermenters and methanogens. The proteins of halophilic bacteria are magnifi cently engineered to function in a milieu containing 2-5 M salt. The proteins and encoding genes of halophiles represent a valuable repository and resource for reconstruction and visualizing processes of habitat selection and adaptive evolution. Search for new enzymes endowed with novel activities and enhanced stability continues to be desirable character for important commercial production. These poly extremophiles are excellent source of enzymes and metabolites possessing inherent ability to function in extreme conditions viz high salt, alkaline pH and facilitating catalysis for biotechnological application in food processing, industrial bioconversion and bioremediation. In brief, we have just begun to realize the great potential and true extent of diversity and suitable industrial applications possible from halophiles.

In an environment consisting of harmful microorganisms, survival of plants mainly depends on effi cient microbial recognition and rapid defense mechanisms. After infection with a necrotizing pathogen, many plants develop resistance against attack by phytopathogens. This resistance is regarded as systemic acquired resistance, which is a key portion of plant defense against pathogen infection. Induction of acquired resistance in plants occurs mainly by enhancement of the levels of pathogenesis-related proteins and salicylic acid. Some groups of plantgrowth-promoting rhizobacteria are involved in an indirect mechanism, either by their antagonistic effect against phytopathogens or by induced systemic resistance (ISR) mechanisms in plants. ISR has been studied with respect to the underlying signaling pathways and to its application in crop protection. The signaling pathway regulating ISR functions independently of salicylic acid, and is mainly dependent on the plant hormones jasmonic acid and ethylene. Apart from these, NPR1, a defensive regulatory protein, is also involved in both systemic and acquired resistance in plants. In this chapter, the molecular and genetic relationship between basal resistance and induced resistance is highlighted.

Two fungal species A. niger and A. parasiticus isolated from agriculture field were used in the present study. These two fungal isolates were studied for the siderophore production on the modified CAS agar medium. On daily observation it was observed that the growth was increased along with the production indicating the change in colour of CAS dye from blue to purplish red by A. niger and Yellow by A. parasiticus. Quantitative determination of siderophore production was further studied using liquid medium. After 10 days of incubation A. niger and A. parasiticus produce 80% and 73% units of siderophore. Chemical determination showed that both the fungal isolates showed hydroxamate type of siderophore. Optimization of type of inoculum showed that block inoculum produced maximum siderophore compared to loop and monosporic inoculation in both the fungal isolates. Neutral pH 7.0 showed maximum siderophore production in both the isolates. Decrease in iron concentration increases the siderophore production by the fungal isolates. Maximum siderophore production 80% and 74% units was observed in A. niger and A. parasiticus respectively when there was no addition of iron in the medium. Pot studies were carried out to observe the effect of fungal inoculum on mungbean plant. Inoculation with fungal isolates showed increase in number of leaves, number of branches, number of lateral roots, plant height, fresh weight and dry weight of plant compared to control. Thus both the fungal isolates proved to be potential bioinoculant for improving the growth of mungbean plant.

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Six Trichoderma strains (collected from IARI, New Delhi and MTCC, Chandigarh) were tested for their ability to inhibit soil-borne pathogen of groundnut mainly Sclerotium rolfsii (causing stem rot on groundnut). In vitro percent growth inhibition of S. rolfsii by various Trichoderma strains were recorded at 5 th day after inoculation (DAI). Results obtained from the antagonism study indicated that Trichoderma viride (NBAII Tv 23) inhibited 61% growth of phytopathogenic fungi S. rolfsii followed by Trichoderma harzianum (NBAII Th1) (55% growth inhibition of pathogen). The specific activities of cell wall degrading enzymes chitinase, β-1,3 glucanase, protease and cellulase were tested during different incubation period (48, 72 and 96 h) when Trichoderma spp. grew in the presence of pathogen cell wall in synthetic media. The antagonist T. viride (NBAII Tv 23) induced higher chitinase and protease activity. The growth inhibition of pathogen during antagonism were positively correlated with coiling pattern of antagonists at 14 th day after inoculation (DAI) as well as with the induction of chitinase, β-1,3 glucanase and total phenol content. However, the amount of cellulase and polygalacturonase recorded was least in these antagonists treatment. A significant positive correlation (p = 0.01) between percentage growth inhibition of test fungus and lytic enzymes (chitinase, β-1,3-glucanase and protease) in the culture medium of antagonist treatment established a relationship to inhibit growth of fungal pathogen by increasing the levels of these enzymes. Among all the tested Trichoderma strains, T. viride (NBAII Tv 23) was found to be the best strain to be used in biological control of plant pathogen S. rolfsii.

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