Effects of halophilic PGPR on salt stress and growth parameters in tomato plants
14th International Molecular Biology and Biotechnology Congress (MolBiotech 2025), 26 December 2025, pp.44-49, (Full Text)
- Publication Type: Conference Paper / Full Text
- Page Numbers: pp.44-49
- Dokuz Eylül University Affiliated: Yes
Abstract
Salt-induced osmotic stress significantly alters membrane structure, enzyme activity, water balance, and metabolic processes by disrupting the intracellular equilibrium of bacteria. Understanding bacterial stress responses to high salinity is crucial in environmental microbiology, food safety and microbial ecology. This study investigated the salt tolerance of six bacterial isolates: Bacillus sp. (EM19), Thalassobacillus devorans (EM34), Bacillus atrophaeus (EK3), Promicromonospora sp. (EM8), Zhihengliuella halotolerans (EM2), and Zhihengliuella salsuginis (EM30) under varying sodium chloride (NaCl) concentrations (1500, 2000, 2500, and 3000 mM). The isolates were incubated for 72 hours at the specified concentrations; growth was assessed via OD600 measurements, and viability was determined through CFU/mL counts. The results showed that increasing salt concentrations significantly reduced the growth rate and viability of most halophilic isolates. However, EM34 and EM8 maintained growth and displayed notable resistance even at 2500–3000 mM NaCl. The discrepancies observed between OD600 and CFU values for these isolates at high salinity may be explained by stress-induced morphological alterations or the presence of damaged yet metabolically active cells which can contribute to optical density without forming colonies. Overall, although elevated NaCl levels generally inhibited bacterial growth and viability, substantial differences in salt tolerance were observed among the isolates. These findings highlight the importance of integrating optical density measurements with culture-based viability assays to obtain a more accurate understanding of bacterial responses to salt stress. Furthermore, the remarkable salt tolerance of certain isolates suggests their potential for biotechnological applications, including food safety, osmoregulation research, and environmental adaptation studies.