Abstract
BackgroundChromobacterium species, through their bioactive molecules, help in combating biotic and abiotic stresses in plants and humans. The present study was aimed to identify, characterize and preserve in natural gums the violet-pigmented bacterial isolate TRFM-24 recovered from the rhizosphere soil of rice collected from Tripura state. ResultsBased on morphological, biochemical and 16S rRNA gene sequencing, the isolate TFRM-24 was identified as Chromobacterium violaceum (NAIMCC-B-02276; MCC 4212). The bacterium is saprophytic, free living and Gram negative. The strain was found positive for production of IAA, cellulase, xylanase and protease, and showed tolerance to salt (2.5%) and drought (-1.2 MPa). However, it showed poor biocontrol activity against soil-borne phytopathogens and nutrient-solubilizing abilitiets. C. violaceum strain TRFM-24 did not survive on tryptic soya agar (TSA) beyond 12 days between 4 and 32 °C temperature hence a method of preservation of this bacterium was attempted using different natural gums namely Acacia nilotica (babul), Anogeissus latifolia (dhavda), Boswellia serrata (salai) and Butea monosperma (palash) under different temperature regime (6–32 °C). The bacterium survived in babul gum (gum acacia), dhavda and salai solution at room temperature beyond a year. ConclusionBased on polyphasic approach, a violet-pigmented isolate TRFM-24 was identified as Chromobacterim violaceum which possessed some attributes of plant and human importance. Further, a simple and low-cost preservation method of strain TRFM-24 at room temperature was developed using natural gums such as babul, dhavda and salai gums which may be the first report to our knowledge.
Highlights
Chromobacterium species, through their bioactive molecules, help in combating biotic and abiotic stresses in plants and humans
Ahmad et al [22] used C. violaceum TRFM-24 as an indicator for detecting tryptophan in the tris-minimal medium supplemented with acid hydrolysed casein hydrolysate to confirm production of indole-3-acetic acid (IAA) by the tryptophanindependent pathway operating in Micrococcus aloeverae DCB-20
The strain TRFM-24 had a short lifespan of 10 days at 4–10 °C and at room temperature and biological oxygen demand (BOD) incubator which supported the earlier work, wherein sensitivity of C. violaceum to low (1–2 days or 4 °C) temperature and at 12 °C was reported [4, 61]. To preserve this bacterium at room temperature, we have developed a bacterial preservation process involving low-cost, watersoluble natural gums namely babul, dhavda and salai to overcome low-temperature stress to increase survivability of the strain TRFM-24
Summary
Chromobacterium species, through their bioactive molecules, help in combating biotic and abiotic stresses in plants and humans. It is important to develop a cost-effective method for stable and long-term preservation of this bacterium to ensure maintenance of its viability and genetic stability considering its multifaceted uses as mentioned above. Natural gums (gums from plants) are hydrophilic carbohydrate polymers of high molecular weights, composed of monosaccharide units joined by glucosidic bonds These gums are either soluble in water or absorb water and swell up or disperse in cold water to give a viscous solution or jelly. The aim of the present study was to (1) identify pigmented bacterium isolated from the rhizosphere soil of Tripura state, (2) characterize it functionally to reveal its plant growth-promoting traits and (3) develop a low-cost and simple method to preserve the C. violaceum TRFM-24 for a considerable period of time without losing its viability and stability
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