Bacterial exopolymeric substances (EPS) are molecules released in response to the physiological stress encountered in the natural environment. EPS are structural components of the extracellular matrix in which cells are embedded during biofilm development. The chemical nature and functions of these EPS are dependent on the genetic expression of the cells within each biofilm. Although some bacterial matrices have been characterized, understanding of the function of the EPS is relatively limited, particularly within the Bacillus genus. Similar gaps of knowledge exist with respect to the chemical composition and specific roles of the macromolecules secreted by Bacillus subtilis in its natural environment. In this review, the different EPS from B. subtilis were classified into four main functional categories: structural (neutral polymers), sorptive (charged polymers), surface-active and active polymers. In addition, current information regarding the genetic expression, production and function of the main polymers secreted by B. subtilis strains, particularly those related to biofilm formation and its architecture, has been compiled. Further characterization of these EPS from B. subtilis remains a challenge.
a b s t r a c tMonumental stone decay is a consequence of the weathering action of physical, chemical and biological factors, which induce a progressive increase in porosity. To cope this degradation, bacterial calcium carbonate mineralization has been proposed as a tool for the conservation of monumental calcareous stones. The advantage of this kind of treatment is to obtain a mineral product similar to the stone substrate, mimicking the natural process responsible for stone formation. In this work, the possibility to induce CaCO 3 mineralization by a bacteria-mediated system in absence of viable cells was investigated and tested on stone. Our results showed that Bacillus subtilis dead cells as wells as its bacterial cell wall fraction (BCF) can act as calcite crystallization nuclei in solution. BCF consolidating capability was further tested in laboratory on slab stones, and in situ on the Angera Church, a valuable 6th century monumental site. New crystals formation was observed inside pores and significant decrease in water absorption (up to 16.7%) in BCF treated samples. A little cohesion increase was observed in the treated area of the Angera Church, showing the potential of this application, even though further improvements are needed.
Aims: The aim of this study was to isolate arsenic‐resistant bacteria from contaminated sediment of the Orbetello Lagoon, Italy, to characterize isolates for As(III), As(V), heavy metals resistance, and from the phylogenetic point of view. Methods and Results: Enrichment cultures were carried out in the presence of 6·75 mmol l−1 of As(III), allowing isolation of ten bacterial strains. Four isolates, ORAs1, ORAs2, ORAs5 and ORAs6, showed minimum inhibitory concentration values equal or superior to 16·68 mmol l−1 and 133·47 mmol l−1 in the presence of As(III) and As(V), respectively. Isolate ORAs2 showed values of 1·8 mmol l−1 in the presence of Cd(II) and 7·7 mmol l−1 of Zn(II), and isolate ORAs1 pointed out a value of 8·0 mmol l−1 in the presence of Cu(II). Analysis of 16S rRNA gene sequences revealed that they can be grouped in the three genera Aeromonas, Bacillus and Pseudomonas. Phylogenetic analysis of the four more arsenic‐resistant strains was also performed. Conclusion: Isolates are highly resistant to both As(III) and As(V) and they could represent good candidates for bioremediation processes of native polluted sediments. Significance and Impact of the Study: This study provides original results on levels of resistance to arsenic and to assigning genera of bacterial strains isolated from arsenic‐polluted sediments.
Biofilms in the industrial environment could be problematic. Encased in extracellular polymeric substances, pathogens within biofilms are significantly more resistant to chlorine and other disinfectants. Recent studies suggest that compounds capable of manipulating nitric oxide-mediated signaling in bacteria could induce dispersal of sessile bacteria and provide a foundation for novel approaches to controlling biofilms formed by some microorganisms. In this work, we compared the ability of five nitric oxide donors (molsidomine, MAHMA NONOate, diethylamine NONOate, diethylamine NONOate diethylammonium salt, spermine NONOate) to dislodge biofilms formed by non-typhoidal Salmonella enterica and pathogenic E. coli on plastic and stainless steel surfaces at different temperatures. All five nitric oxide donors induced significant (35-80%) dispersal of biofilms, however, the degree of dispersal and the optimal dispersal conditions varied. MAHMA NONOate and molsidomine were strong dispersants of the Salmonella biofilms formed on polystyrene. Importantly, molsidomine induced dispersal of up to 50% of the pre-formed Salmonella biofilm at 4°C, suggesting that it could be effective even under refrigerated conditions. Biofilms formed by E. coli O157:H7 were also significantly dispersed. Nitric oxide donor molecules were highly active within 6 hours of application. To better understand mode of action of these compounds, we identified Salmonella genomic region recA-hydN, deletion of which led to an insensitivity to the nitric oxide donors.
Although the implications of calcium carbonate (CaCO(3)) precipitation by microorganisms in natural environments are quite relevant, the physiology and genetics of this phenomenon are poorly understood. We have chosen Bacillus subtilis 168 as our model to study which physiological aspects are associated with CaCO(3) (calcite) formation during biofilm development when grown on precipitation medium. A B. subtilis eftA mutant named FBC5 impaired in calcite precipitation was used for comparative studies. Our results demonstrate that inactivation of etfA causes a decrease in the pH of the precipitation medium during biofilm development. Further analysis demonstrated that eftA extrudes an excess of 0.7 mol H(+) L(-1) with respect to B. subtilis 168 strain. Using media buffered at different pH values, we were able to control calcite formation. Because etfA encodes the alpha-subunit of a putative flavoprotein involved in fatty acid metabolism, we compared the intracellular levels of NADH among strains. Our physiological assay showed that FBC5 accumulated up to 32 times more NADH than the wild-type strain. We propose that the accumulation of NADH causes a deregulation in the generation of the proton motive force (DeltamicroH(+)) in FBC5 producing the acidification.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.