Isolation And Identification Of Bacterial Isolates: Case Study

3.1. Isolation and identification of Bacterial isolates
An enrichment culture technique was used for the isolation of bacteria responsible for biodegradation of phorate in soil. Screening of these bacterial species for phorate degradation in liquid cultures in our previous study (Jariyal et al., 2014), resulted in identification of bacterial species B. aerophilus strain Imbl 4.1 , Brevibacterium frigoritolerans strain Imbl 2.1 and Pseudomonas fulva strain Imbl 5.1. However, these bacterial species, causing complete phorate degradation within 7 days were considered most potent phorate degraders and hence selected for further studies on optimizing their bioremediation potential in agricultural soils Taxonomic identity is established through
100,200, 300 mg kg-1. These were extracted, cleaned and analyzed following the method already described. The control samples from untreated plots and reagent blanks were also processed in the same way to determine the interferences, if any, due to the substrate and reagents, respectively. The mean percent recovery of phorate and its metabolites viz. (sulfone, sulfoxide and phoratoxon) from the fortified samples were found to be more than 85 per cent. Therefore, the results have been presented as such without applying any correction factor. Limit of quantification (LOQ) and limit of detection (LOD) of phorate in soil were found to be 0.01 and 0.003 mg kg-1, respectively.
3.2. Comparative analysis of bacterial spp. for phorate degradation in liquid cultures
In our previous study (Jariyal et al., 2014), comparative analysis identified bacterial species Brevibacterium frigoritolerans, Bacillus aerophilus and Pseudomonas fulva as most potent phorate degrader, caused complete metabolization of phorate in 13 day. In view of the above, the phorate degradation ability of these bacterial strain could be arranged as Pseudomonas fulva strain Imbl 5.1> Bacillus aerophilus strain Imbl 4.1> Brevibacterium frigoritolerans strain Imbl 2.1. In view of the above, further studies on phorate metabolization in soil were conducted using these bacterial species.
3.3. Phorate metabolization by bacterial isolates in phorate amended
Recently, Rana et al., (2015) used Bacillus aerophilus for thiamethoxam degradation, whereas Sharma et al., (2014) degrade imidachlorpid by Bacillus alkalinitrilicus. Soil microbes viz. Bacillus firmus and Bacillus thuringiensis were found to be effective in degradation of fipronil (Mandal 2013, 2014). Rani and Juwarkar, (2012) observed a lower degradation of 55 per cent of phorate in sandy loam soils by a bacterial consortium consisting of R. eutropha, Pseudomonas aeruginosa and Enterobacter cloacae. Such phorate degradation is associated with a parallel increase in sulphoxide and sulpohone as toxic phorate metabolites (Venkatramesh et al., 1987). Similarly, with other microbial species, identified phorate metabolites included phosphodithioate sulphoxide, phosphodithioate sulphone, diethyl dithiophosphate, triethyl dithio-phosphate, diethyl disulfide, formaldehyde and hydrogen sulfide (Hong et al., 2000; Hong and Pehkonen, 1998; Kadam and Gangawane 2005; Singh et al., 2003; Szeto et al., 1990). Thus, the degradation products differ with different microbial species producing different metabolites some of which are far more toxic than the parent compound (Henderson et