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Introduction
Rice (Oryza sativa) is a major cash crop that has been cultivated for more than 7000 years and represents the staple food in different parts of the world (Lakshmanan et al. 2015). Rice is known to be grown in watery environments. The upper surface of paddy soil density is considered very important for good crop production (Kazemi et al. 2010).
Rhizosphere is the zone of soil in close proximity to the surface of plant root (Morgan et al. 2005). The rhizosphere is colonized by huge and diverse microbial community where the microbial cell density may exceed cell density of the plants itself. The plant-associated microorganisms are known as plant microbiome. The rhizospheric microbiome may harbor viruses, bacteria, fungi, protozoa, and nematodes, thus making the rhizosphere a very dynamic environment (Barea et al. 2005). The plant secretes a number of compounds collectively known as exudates through its roots to the rhizosphere which may include sugars, organic acids, vitamins, hormones, enzymes, and secondary metabolites (Berendsen et al. 2012; Huang et al. 2014). The microbiome, on the other hand, influence seed germination, seedling vigor, nutrients uptake, plant growth and development, and plant health and resistance to diseases (de Zelicourt et al. 2013; Osorio Vega 2007).
Mesophilic bacteria grow at moderate temperature i.e., 25-40°C with optimal growth occurs at 37°C (normal body temperature) and most of the pathogenic bacteria belong to this group. Representative mesophilic bacteria include Streptococcus pneumonia, Streptococcis pyroenes, Staphylococcus aureus, Escherichia coli, etc. Mesophilic bacteria are used in various biotechnological applications such as production of vinegar, yogurt, bread, cheese, amino acids, lactic acid and antibiotics production (streptomycin, erythromycin, chloromycetin, terramycin, tetracycline) (Shi and Zhu 2009), biodegradation of the environmental pollutants (Salt et al. 1998), and production of industrially and medically important enzymes such as amylase, cellulase, lipase, xylanase, arginase, L-asparagase (Turner et al. 2007). Rhizospheric bacteria also have wide range of applications in agriculture, and ecology. For instance, Plant Growth Promoting Rhizobacteria (PGPR) is used in agriculture to improve plant health and productivity or as pesticides and fertilizers (Josic and Kovač 2008). In this context, rhizospheric soil of rice plant may host diverse microbial community with potential industrial and agricultural applications (Muangham et al. 2019).
The present work aimed at isolation...