Viable but Nonculturable State of Yeast Candida sp. Strain LN1 Induced by High Phenol Concentrations

Abstract

Microbial degradation plays an important role in the environmental remediation. However, most microorganisms’ pollutant-degrading capability is weakened due to their entry into a viable but non-culturable (VBNC) state. Despite there is some evidence for the VBNC state of pollutant-degrading bacteria, limited studies have been conducted to investigate the VBNC state of pollutant degraders among fungi. In this work, the morphological, physiological and molecular changes of a phenol-degrading yeast strain LN1 exposed to high phenol concentrations were investigated. The results confirmed that Candida sp. strain LN1, which possessed highly efficient capability in degrading 1000 mg/L of phenol, as well as high potential for aromatic compounds degradation, entered into the VBNC state after 14 h of incubation at 6000 mg/L phenol. Resuscitation of VBNC cells can restore their phenol degradation performance. Compared to normal cells, significant dwarfing, surface damage and physiological changes of VBNC cells were observed. Molecular analysis indicated that the down-regulated genes were related to oxidative stress response, xenobiotics degradation, carbohydrate and energy metabolism, whereas the up-regulated genes were related to RNA polymerase, amino acid metabolism, DNA replication and repair. This report revealed that a pollutant-degrading yeast strain entered into the VBNC state under high concentrations of contaminants, providing new insights into its survival status and bioremediation potential under stress. Importance The viable but non-culturable (VBNC) state is known to affect the culturability and activity of microorganisms. However, limited studies have been conducted to investigate the VBNC state of other pollutant degraders such as fungi. In this study, the VBNC state of a phenol-degrading yeast strain was discovered. In addition, comprehensive analysis of the morphological, physiological and molecular changes of the VBNC cells were performed. This study provides new insight into the VBNC state of pollutant degraders, and how they restored the activities that was inhibited by stressful conditions. Enhanced bioremediation performance of indigenous microorganisms could be expected by preventing and controlling the formation of VBNC state.

Comparative Analysis Using Raman Spectroscopy of the Cellular Constituents of Lacticaseibacillus paracasei Zhang in a Normal and Viable but Nonculturable State

“…Carbohydrates are the most important constituents for discriminating between cell states, and they are the energy source used to maintain cell activity [ 44 ]. The variation in Raman peaks attributed to carbohydrates was analyzed.…”

“…Previous reports found that several genes involved in carbohydrate and energy metabolism in yeast and bacteria were downregulated in the VBNC state [ 12 , 45 ]. However, different stress conditions and microbial species exhibited different changes in their carbohydrate metabolism [ 44 ].…”

Insights Into Mechanism of the Naphthalene-Enhanced Biodegradation of Phenanthrene by Pseudomonas sp. SL-6 Based on Omics Analysis

“…Meanwhile, there was no significant difference in biomass between the two group. Many functional microbial populations enter viable but non-culturable (VBNC) state ( Xie et al, 2021 ) under unfavorable conditions to deal with environmental stresses, including oligotrophic nutrients and high concentration of pollutants ( Su et al, 2021 ). Under the conditions of NAP or/and PHE as carbon sources, SL-6 didn’t show an obvious growth comparing to growing on LB ( Supplementary Figure 1 ).…”

Contribution of Particulates to Airborne Disease Transmission and Severity: A Review

“…These properties of VBNC cells are more important in determining their potential influence on human health, as their resistance to harsh environments allows them to remain viable during transport over long distances . Although there have been several reports of fungi being found in the VBNC state, VBNC cells generally refer to bacteria. − Li et al (2014) identified 51 human pathogens capable of existing in the VBNC state, suggesting that numerous other microorganisms may have the same pattern of physiological activity . Notably, Legionella bacteria, which enter the VBNC state under conditions of nutritional deficiency, have been found to maintain infectivity for over a year .…”