Transcriptional modulation of Porphyromonas gingivalis biofilms on titanium-copper implant surfaces

The healthcare sector is currently concerned about infections caused by Porphyromonas gingivalis biofilms due to their high frequency and incidence, particularly in patients with implanted medical devices. This study investigated biofilm formation and biofilm-related gene expression in P. gingivalis on titanium-copper discs and polycarbonate discs. P. gingivalis highly expressed biofilm-related genes were examined using quantitative real-time PCR during biofilm formation on the Ti-Cu surface. SEM analysis revealed various cellular components around the aggregated cells at various stages of biofilm formation. The Ti-Cu surface was colonized by P. gingivalis, as evidenced by biofilm formation levels that varied from ~ 103-104 CFU/cm2 after 2 days of incubation to ~ 105-107 CFU/cm2 after 7 days. Real-time expression analysis showed a significant increase in the expression of signaling molecules on Ti-Cu discs. Furthermore, genes linked to virulence (rgpA, rgpB, and Kgp, fimC, PorK, and PorP) and adhesion (mfa1, fimD, fimA, RpoN, rgpA, rgpBiKgp) demonstrate transcriptional alterations in signaling pathways impacting P. gingivalis biofilm on Ti-Cu surfaces. Scanning electron microscopy (SEM) and confocal microscopy correlated the results of the structural analysis with the expression from the qPCR data. This study adds significant value by advancing the understanding of biofilm formation on Ti-Cu implants.

The Pleiotropic Phenotypes Caused by an hfq Null Mutation in Vibrio harveyi

Hfq is a global regulator and can be involved in multiple cellular processes by assisting small regulatory RNAs (sRNAs) to target mRNAs. To gain insight into the virulence regulation of Hfq in Vibrio harveyi, the hfq null mutant, ∆hfq, was constructed in V. harveyi strain 345. Compared with the wild-type strain, the mortality of pearl gentian sharply declined from 80% to 0% in ∆hfq when infected with a dose that was 7.5-fold the median lethal dose (LD50). Additionally, ∆hfq led to impairments of bacterial growth, motility, and biofilm formation and resistance to reactive oxygen species, chloramphenicol, and florfenicol. A transcriptome analysis indicated that the expression of 16.39% genes on V. harveyi 345 were significantly changed after the deletion of hfq. Without Hfq, the virulence-related pathways, including flagellar assembly and bacterial chemotaxis, were repressed. Moreover, eleven sRNAs, including sRNA0405, sRNA0078, sRNA0419, sRNA0145, and sRNA0097, which, respectively, are involved in chloramphenicol/florfenicol resistance, outer membrane protein synthesis, electron transport, amino acid metabolism, and biofilm formation, were significantly down-regulated. In general, Hfq contributes to the virulence of V. harveyi 345 probably via positively regulating bacterial motility and biofilm formation. It is involved in flagellar assembly and bacterial chemotaxis by binding sRNAs and regulating the target mRNAs.

New Strategies for Biocontrol of Bacterial Toxins and Virulence: Focusing on Quorum-Sensing Interference and Biofilm Inhibition

The overuse of antibiotics and the emergence of multiple-antibiotic-resistant pathogens are becoming a serious threat to health security and the economy. Reducing antimicrobial resistance requires replacing antibiotic consumption with more biocontrol strategies to improve the immunity of animals and humans. Probiotics and medicinal plants have been used as alternative treatments or preventative therapies for a variety of diseases caused by bacterial infections. Therefore, we reviewed some of the anti-virulence and bacterial toxin-inhibiting strategies that are currently being developed; this review covers strategies focused on quenching pathogen quorum sensing (QS) systems, the disruption of biofilm formation and bacterial toxin neutralization. It highlights the probable mechanism of action for probiotics and medicinal plants. Although further research is needed before a definitive statement can be made on the efficacy of any of these interventions, the current literature offers new hope and a new tool in the arsenal in the fight against bacterial virulence factors and bacterial toxins.

The Determination, Monitoring, Molecular Mechanisms and Formation of Biofilm in E. coli

Biofilms are cell assemblies embedded in an exopolysaccharide matrix formed by microorganisms of a single or many different species. This matrix in which they are embedded protects the bacteria from external influences and antimicrobial effects. The biofilm structure that microorganisms form to protect themselves from harsh environmental conditions and survive is found in nature in many different environments. These environments where biofilm formation occurs have in common that they are in contact with fluids. The gene expression of bacteria in complex biofilm differs from that of bacteria in the planktonic state. The differences in biofilm cell expression are one of the effects of community life. Means of quorum sensing, bacteria can act in coordination with each other. At the same time, while biofilm formation provides many benefits to bacteria, it has positive and negative effects in many different areas. Depending on where they occur, biofilms can cause serious health problems, contamination risks, corrosion, and heat and efficiency losses. However, they can also be used in water treatment plants, bioremediation, and energy production with microbial fuel cells. In this review, the basic steps of biofilm formation and biofilm regulation in the model organism Escherichia coli were discussed. Finally, the methods by which biofilm formation can be detected and monitored were briefly discussed.

Allelic variation of Escherichia coli outer membrane protein A: Impact on cell surface properties, stress tolerance and allele distribution

Outer membrane protein A (OmpA) is one of the most abundant outer membrane proteins of Gram-negative bacteria and is known to have patterns of sequence variations at certain amino acids-allelic variation-in Escherichia coli. Here we subjected seven exemplar OmpA alleles expressed in a K-12 (MG1655) ΔompA background to further characterization. These alleles were observed to significantly impact cell surface charge (zeta potential), cell surface hydrophobicity, biofilm formation, sensitivity to killing by neutrophil elastase, and specific growth rate at 42°C and in the presence of acetate, demonstrating that OmpA is an attractive target for engineering cell surface properties and industrial phenotypes. It was also observed that cell surface charge and biofilm formation both significantly correlate with cell surface hydrophobicity, a cell property that is increasingly intriguing for bioproduction. While there was poor alignment between the observed experimental values relative to the known sequence variation, differences in hydrophobicity and biofilm formation did correspond to the identity of residue 203 (N vs T), located within the proposed dimerization domain. The relative abundance of the (I, δ) allele was increased in extraintestinal pathogenic E. coli (ExPEC) isolates relative to environmental isolates, with a corresponding decrease in (I, α) alleles in ExPEC relative to environmental isolates. The (I, α) and (I, δ) alleles differ at positions 203 and 251. Variations in distribution were also observed among ExPEC types and phylotypes. Thus, OmpA allelic variation and its influence on OmpA function warrant further investigation.

Clinical Escherichia coli: From Biofilm Formation to New Antibiofilm Strategies

Escherichia coli is one of the species most frequently involved in biofilm-related diseases, being especially important in urinary tract infections, causing relapses or chronic infections. Compared to their planktonic analogues, biofilms confer to the bacteria the capacity to be up to 1000-fold more resistant to antibiotics and to evade the action of the host’s immune system. For this reason, biofilm-related infections are very difficult to treat. To develop new strategies against biofilms, it is important to know the mechanisms involved in their formation. In this review, the different steps of biofilm formation in E. coli, the mechanisms of tolerance to antimicrobials and new compounds and strategies to combat biofilms are discussed.

Simulation of bacterial biofilms and estimation of the sensitivity of healthcare-associated infection pathogens to bactericide Sekusept active

The effect of bactericide Sekusept active (B SA), a peracetic acid-based preparation, on microbial strains, isolated from patients with severe infectious diseases who were treated in a regional children's multi-specialty hospital, was studied. Based on the biochemical identification, the strains were classified as gram-negative non-fermenting bacteria (22 strains), Enterobacteriaceae family (18 strains), and bacilli - 3 strains. The biocidal activity of B SA was evaluated by the degree of inhibition of the growth of bacterial cells, existing in the planktonic form and in the form of biofilm (on a flat-bottomed plastic immunological tablet). It was shown that all the studied strains had the ability to biofilm formation, most of them (67,4%) formed moderately pronounced biofilms, and non-fermenting bacteria had a particularly pronounced coefficient of biofilm formation. The selected concentrations of B CA inhibited the growth of planktonic cells, and the ability of bactericide to prevent the formation of biofilms depended on the concentration (the most effective concentrations were 0,8 and 3,0%). Sensitivity of the strains existed in the aged biofilm to the bactericide was significantly lower, especially resistant to this effect were biofilms formed by non-fermenting bacteria and representatives of fam. Enterobacteriaceae. Our results confirm the importance of testing the effectiveness of biocides not only in accordance with standard methods developed for microorganisms in planktonic form, but also for biofilms.

Bacterial response mechanism during biofilm growth on different metal material substrates: EPS characteristics, oxidative stress and molecular regulatory network analysis

Overwhelming growth of bacterial biofilms on different metal-based pipeline materials are intractable and pose a serious threat to public health when tap water flows though these pipelines. Indeed, the underlying mechanism of biofilm growth on the surface of different pipeline materials deserves detailed exploration to provide subsequent implementation strategies for biofilm control. Thus, in this study, how bacteria response to their encounters was explored, when they inhabit different metal-based pipeline substrates. Results revealed that bacteria proliferated when they grew on stainless steel (SS) and titanium sheet (Ti), quickly developing into bacterial biofilms. In contrast, the abundance of bacteria on copper (Cu) and nickel foam (Ni) substates decreased sharply by 4-5 logs within 24 h. The morphological shrinkage and shortening of bacterial cells, as well as a sudden 64-fold increase of carbohydrate content in extracellular polymeric substances (EPS), were observed on Cu substrate. Furthermore, generation of reactive oxygen species and fluctuation of enzymatic activity demonstrated the destruction of redox equilibrium in bacteria. Bacteria cultured on Cu substrate showed the strongest response, followed by Ni, SS and Ti. The oxidative stress increased quickly during the growth of bacterial biofilm, and almost all tested metal transporter-related genes were upregulated by 2-11 folds on Cu, which were higher than on other substrates (1-2 folds for SS and Ti, 2-9 folds for Ni). Finally, these behaviors were compared under the biofilm regulatory molecular network. This work may facilitate better understanding different response mechanisms during bacterial biofilm colonization on metal-based pipelines and provide implications for subsequent biofilm control.