Thirumala Mothe

Salt-tolerant plant growth-promoting (PGP) actinobacteria play an important role in enhancing plant tolerance to salinity stress and improving crop productivity. Here, 9 morphologically distinct actinobacterial isolates (A-I) were isolated from the rhizosphere soil of Oryza sativa cultivated in the Nalgonda district, Telangana, screened for PGP characteristics (nitrogen fixation, indole-3-acetic acid production (IAA), and phosphate solubilisation) and salt tolerance. Among them, isolate H exhibited superior PGP activity and salt tolerance, growing in media containing up to 10% NaCl. Hence, it was selected for further work. Isolate H produced cellulase, lipase, amylase and showed a positive catalase reaction. It utilised glucose, fructose, galactose, and sucrose, but not maltose. Antibiotic susceptibility analysis indicated that isolate H was partially resistant to penicillin but sensitive to tetracycline, ciprofloxacin, and vancomycin. Molecular identification based on 16S rDNA sequencing (1,356 bp) revealed that isolate H shared 99.78% sequence similarity and 99% query coverage with Streptomyces levis NBRC 15423(T), suggesting that the isolate belongs to the genus Streptomyces. Seed germination efficiency (%) revealed that the 24 hrs culture (T1) of isolate H had a significantly greater effect on rice seed germination than the 48 hrs culture (T2). The germination rate of rice seeds in T1 was 86.67%, followed by T2 (72.00%), the control (62.33%), and distilled water (55.67%), indicating that the 24 hrs grown culture of isolate H may be used to enhance rice seed germination under salt stress. This study provides preliminary evidence of the potential of a Streptomyces levis strain as a PGP bacterium under saline conditions.

Vanillin is widely used as a food flavouring, scent ingredient in cosmetics and perfumes, as an intermediate in agrochemicals & medicines and also as a nutraceutical. Serial dilution of sediment sample yielded 32 strains, among which three isolates A2, A7, and 04 reported here were characterized at molecular level by 16S rDNA sequencing. They were identified and similar to Pseudomonas aeruginosa (94.97%), Acinetobacter baumannii (99.93%) and Lysinibacillus macroides (98.67%) respectively based on its 16S rDNA sequences. Among these three strains, isolate 04 was with high ferulic acid (FA) to vanillin bioconversion activity. Vanillin concentration was determined by the Thiobarbituric acid (TBA) method and analysed by UV-spectrophotometry, which showed 11.63 ± 0.05 mg/ml vanillin after optimization studies. HPLC with UV detector was also used for the characterization of the vanillin formed, which showed peak at 8.793 rt. To improve FA to vanillin bioconversion, physical mutagenesis was performed on isolate 04, which generated three mutants (1, 2, and 3). These three mutants were subject to FA to vanillin biotransformation study. TBA method and UV spectrophotometric analysis showed a higher conversion by mutant 2 than other two mutants, 1 and 3. Mutant 2 formed almost two-fold vanillin i.e. 19.78 ± 0.05 mg/ml when compared to its wild strain, isolate 04. Hence, this mutant may be further subjected to optimization studies and exploited for industrial biotransformation process.

Nine actinobacterial isolates were purified from the sediment sample of Kogilvai village, Warangal, Telangana, based on their capability to grow on the minimal medium with Ferulic acid (FA) as only Carbon (C) source. FA to Vanillin conversion capacity of these isolates was identified by Thin-layer chromatography (TLC). Biotransformation of FA to Vanillin was high by four isolates, S1, S3, O3 and O4 when compared to other five isolates (O1, O2, S2, S4 and S5) with initial pH 7 in basal medium. Among these four isolates, optimal and rapid FA to Vanillin bioconversion of 140 mg/L was shown by isolate S1 with UV-spectrophotometry. Its conversion was confirmed by High Performance Liquid Chromatography (HPLC) analysis with retention time of 2.9 min after 28hrs of incubation at 37°C with 1g/L ferulic acid in the medium with 150 rpm. Isolate S1 could utilize Lactose, Maltose, Glycerol, Fructose, Galactose, Sucrose, Dextrose, L-Arabinose, ONPG, Esculin and not other carbohydrates present in the Himedia Hicarbo kit. Molecular characterization showed that 16S rDNA gene sequence of isolate S1 was 98.27% similar to Limosilactobacillus fermentum CECT 562 with completeness of 96.7% and was identified as Limosilactobacillus sp. 16S rDNA gene sequence of isolate S1 was submitted to NCBI GenBank and its accession number was OR136396. As this isolate has high potential of FA to Vanillin biotransformation capacity, it can be further explored to be used for industrial setups for commercial exploitation.

Consuming of water contaminated with high fluoride concentration for a very long time causes health problems such as, dental and skeletal fluorosis. Hence, defluoridation of water is essentially required before consumption, when water is contaminated with high fluoride concentration. In this present study, research was focussed on to isolate bacteria which are showing fluoride resistantance from samples of ground water from high fluoride affected regions of Nalgonda. After analysis of 10 samples from different areas of Nalgonda district, two samples of ground water from Narketpally and Nampally showed the high fluoride concentrations of 9.18 ppm and 7.55 ppm respectively. Hence, in the present study, Narketpally ground water sample with highest ppm was considered to isolate fluoride resistant bacteria. A total of eight fluoride resistant organisms were purified from this sample with varying fluoride resistance on Luria Bertani agar with varying fluoride concentraion from 25mg/L to 600mg/L at pH 7. Among the eight strains isolated, three strains MB1, F and G were showing high fluoride resistance (up to 500mg/L), which were further explored for their role in bioremediation of fluoride. In batch mode study, MB1 strain showed high fluoride degradation of 68%, whereas, F and G strains showed 57% and 44%fluoride removal, respectively, when fluoride concentration was present at 20 mgL-1 at 30 °C temperature and pH 7, with dextrose (10 g) utilised as source of carbon per 100 mL media after incubation of 8 days. Results indicate that, MB1 possibly a potential fluoride resistant bacterium with high fluoride bioremediation capacity.

A novel Gram-stain-positive, rod-shaped, motile and endospore-forming novel bacterial strain 25nlg^T was isolated from Lonar soda lake, in India. Based on the 16S rRNA gene sequence analysis, it was identified as a member of Firmicutes, being most closely related to Bacillus patagoniensis PAT 05^T (96.6 %) and other members in the genus Bacillus (T was catalase and oxidase-positive. The strain grows optimally at a pH of 9.5 with 4–6 % (w/v) NaCl and temperature of 35–37 °C. The cell wall of the strain 25nlg^T contains meso-diaminopimelic acid as the diagnostic amino acid. Polar lipids include diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, an unknown phospholipid (PL2), an aminophospholipid (APL2) and three unknown lipids (L2–4). The predominant isoprenoid quinone was MK-7. iso-C_15:0 (41.7 %) was the predominant fatty acid, and significant proportions of anteiso-C_15:0 (20.8 %), C_12:0 (5.5 %), anteiso-C_17:0 (4.9 %), iso-C_17:0 (4.5 %) were also detected in the strain 25nlg^T. The DNA G+C content of the strain 25nlg^T was 40.5 mol%. The results of molecular, physiological and biochemical tests allowed a clear phenotypic differentiation of strain 25nlg^T from all other members of the genus Bacillus. Strain 25nlg^T represents a novel member of the genus Bacillus, for which the name Bacillus lonarensis sp. nov. is proposed. The type strain is 25nlg^T (=KCTC 33413^T = LMG 27974^T = CGMCC = 1.12817^T).