Halotolerant Exiguobacterium profundum PHM11 Tolerate Salinity by Accumulating L-Proline and Fine-Tuning Gene Expression Profiles of Related Metabolic Pathways

Abstract

Salinity stress is one of the serious factors, limiting production of major agricultural crops; especially, in sodic soils. A number of approaches are being applied to mitigate the salt-induced adverse effects in agricultural crops through implying different halotolerant microbes. In this aspect, a halotolerant, Exiguobacterium profundum PHM11 was evaluated under eight different salinity regimes; 100, 250, 500, 1000, 1500, 2000, 2500, and 3000 mM to know its inherent salt tolerance limits and salt-induced consequences affecting its natural metabolism. Based on the stoichiometric growth kinetics; 100 and 1500 mM concentrations were selected as optimal and minimal performance limits for PHM11. To know, how salt stress affects the expression profiles of regulatory genes of its key metabolic pathways, and total production of important metabolites; biomass, carotenoids, beta-carotene production, IAA and proline contents, and expression profiles of key genes affecting the protein folding, structural adaptations, transportation across the cell membrane, stress tolerance, carotenoids, IAA and mannitol production in PHM11 were studied under 100 and 1500 mM salinity. E. profundum PHM11 showed maximum and minimum growth, biomass and metabolite production at 100 and 1500 mM salinity respectively. Salt-induced fine-tuning of expression profiles of key genes of stress pathways was determined in halotolerant bacterium PHM11.

Optimization of submerged fermentation process for improved production of β-carotene by Exiguobacterium acetylicum S01

“…In agreement with our results from an earlier study, the expression levels of carotenogenic genes (CrtI and CrtB) were differentially expressed in X. dendrorhous grown on fermentable carbon sources (Wozniak et al., 2011). Our results supported by the previous study the up-regulation of phytoene desaturase ( pd ) and phytoene synthase ( ps ) in E. profundum PHM11 under stress conditions (Patel et al., 2018). However, pH and temperature are the most important environmental factors affecting the growth and development of bacteria.…”

“…Among the bacterial genera, Exiguobacterium sp. is well-known for the production of β-carotene, astaxanthin, and xanthophylls, respectively (Patel et al., 2018; Sasidharan et al., 2013; Shatila et al., 2013). In the present study, the one-factor-at-a-time optimization results suggested that the adequate concentration of glucose in the fermentation medium would facilitate the enhancement of β-carotene production by E. acetylicum S01, for the first time.…”

“…These include bacterial strains belonging to Bacillus , Exiguobacterium, Corynebacterium and Rhodococcus , the microalgae Haematococcus and Dunaliella , the fungus Blakeslea trispora and yeasts, among others of the genera Rhodotorula, Sporobolomyces, and Phaffia (Venil et al., 2013; Johnson and Schroeder, 1996; Nelis and DeLeenheer, 1991). Hitherto, few carotenoids in the genus Exiguobacterium have been reported (e.g., β-carotene produced by Exiguobacterium profundum PHM11 (Patel et al., 2018), xanthophylls, produced by Exiguobacterium aurantiacum FH (Sasidharan et al., 2013), and astaxanthin, produced by Exiguobacterium sp. (Shatila et al., 2013).…”

Pan‐genome analysis of Exiguobacterium reveals species delineation and genomic similarity with Exiguobacterium profundum PHM 11

“…The bacterial genus Exiguobacterium contains several versatile species isolated from variable extreme environments (Collins et al, 1983;Vishnivetskaya et al, 2009;Vishnivetskaya et al, 2014). Their ability to grow over a wide range of temperatures (−12 to 55 C) and salinity makes them a suitable candidate for developing agriculturally, industrially and environmentally relevant products (Patel et al, 2018;Srivastava et al, 2019a,b). Keeping in view of its unique nature and growth over a wide range of environmental conditions and agriculture relevance, we performed the whole genome sequencing of E. profundum PHM11.The current study indicated that the rRNAsequences in Exiguobacterium whole-genome sequences varied from 4 (E. profundum PHM11) to 28 rRNA sequences (E. aurantiacum DSM6208) with minor sequence variations (Table 1).…”

“…Similar observations have been documented by other researchers working with different species of Exiguobacterium spp. (Cabria et al ., 2014; Vishnivetskaya et al ., 2014; Patel et al ., 2018). Finally, the shared pathways were compared which showed that E. profundum PHM11 shared maximum pathways (138) with E. aurantiacum DSM6208 out of 165 pathways (Supplementary Table 6).…”