Morphological and structural response of Bacillus sp. SFC 500‐1E after Cr(VI) and phenol treatment

Abstract

Bacillus sp. SFC 500‐1E, a bacterial strain isolated from tannery sediments, is able to remove Cr(VI) and simultaneously tolerate high concentrations of phenol. In this study, we used high‐resolution microscopies, fluorescence polarization techniques, and several biochemical approaches to improve our understanding about the adaptive mechanisms of this strain to survive in the presence of Cr(VI) and phenol, both individually and simultaneously. Among adaptive strategies developed by Bacillus sp. SFC 500‐1E, an increase in bacterial size, such as length, width, and height, and ultrastructural alterations, such as electron‐dense precipitates, the presence of exopolymers, and cell lysis, are noteworthy. The exopolymers observed were consistent with the extensive biofilm formation and exopolysaccharides and extracellular protein quantification. At the cell membrane level, a rapid rigidity was induced in Cr(VI) + phenol treatment. This effect was counteracted after 16 h by changes at the level of phospholipids, mainly in the composition of fatty acids (FAs); in particular, an increase in the unsaturated fatty acid/saturated fatty acid ratio was detected. This study shows evidence of some adaptive responses displayed by Bacillus sp. SFC 500‐1E, which allows it to survive in stressful conditions.

Proteomic analysis to unravel the biochemical mechanisms triggered by Bacillus toyonensis SFC 500-1E under chromium(VI) and phenol stress

“…Taken together with previous studies, we can suggest that the increased spo0A levels found in this work could be related to the increase in the EPS content and in the bio lm formation previously described for B. toyonensis SFC 500-1E cells exposed to Cr(VI) + phenol (Fernandez et al 2020). Moreover, Cr(VI) and Cr(III) biosorption, either surface sorption and accumulation within cells, have been other adaptive responses previously reported for this strain (Ontañon et al, 2018b).…”

“…Clp, a protease that functions in preventing cytoplasmic proteins aggregation and maintaining their quality (Santos et Taken together, the presented data provide clear evidence that the presence of phenol [Cr(VI) + phenol treatment] would trigger a more complete global stress response to deal with DNA and protein damage. We have previously demonstrate that B. toyonensis SFC 500-1E is unable to metabolize phenol (Fernandez et al, 2020;Ontañon et al, 2015), and the present proteomic study did not reveal enzymes involved in the aerobic degradation pathways of this compound. Thus, it could result toxic for the cell and would explain the special effort made by the strain to cope the damage.…”

“…Moreover, these changes in the abundance of proteins associated with fatty acid biosynthesis were highly expected and possibly they were needed to reorganize cellular membranes, due to toxic compounds that can change the uidity of bacterial membranes (Murínová and Dercová 2014). In fact, a decrease in B. toyonensis SFC 500-1E membrane uidity or a greater rigidity caused by Cr(VI) + phenol exposure was detected in a previous study (Fernandez et al 2020).…”

“…In this sense, the exopolysaccharide (EPS) matrix as a constituent part provides the scaffold bonding together spores and vegetative cells, as well as protecting to vegetative cells against different stresses (Dawson et al 2012). A previous study performed with B. toyonensis SFC 500-1E shown a signi cantly increase in the EPS content and in the bio lm formation when cells were exposed to Cr(VI) + phenol (Fernandez et al 2020), which could be related to the increased spo0A levels found in this work.…”

Antibiotic and Heavy Metal Co-Resistant Strain Isolated from Enrichment Culture of Marine Sediments, with Potential for Environmental Bioremediation Applications

“…Bacteria tend to form biofilms under different pressures that include the presence of toxic substances such as antibiotics and heavy metals, as well as oxygen limitation [ 40 ]. Bacillaceae strains had been reported to resist stress from heavy metals by forming biofilms [ 41 ]. The biofilm formation is a defense mechanism for bacteria, which can increase the survival rate of these bacteria under stress [ 42 ].…”