Mechanisms of post-transcriptional gene regulation in bacterial biofilms

Understanding the transition to viable but non-culturable state in Escherichia coli W3110: a comprehensive analysis of potential spectrochemical biomarkers

The viable but non-culturable (VBNC) state is considered a survival strategy employed by bacteria to endure stressful conditions, allowing them to stay alive. Bacteria in this state remain unnoticed in live cell counts as they cannot proliferate in standard culture media. VBNC cells pose a significant health risk because they retain their virulence and can revive when conditions normalize. Hence, it is crucial to develop fast, reliable, and cost-effective methods to detect bacteria in the VBNC state, particularly in the context of public health, food safety, and microbial control assessments. This research examined the biomolecular changes in Escherichia coli W3110 induced into the VBNC state in artificial seawater under three different stress conditions (temperature, metal, and antibiotic). Initially, confirmation of VBNC cells under various stresses was done using fluorescence microscopy and plate counts. Subsequently, lipid peroxidation was assessed through the TBARS assay, revealing a notable increase in peroxidation end-products in VBNC cells compared to controls. ATR-FTIR spectroscopy and chemomometrics were employed to analyze biomolecular changes, uncovering significant spectral differences in RNA, protein, and nucleic acid concentrations in VBNC cells compared to controls. Notably, RNA levels increased, while protein and nucleic acid amounts decreased. ROC analyses identified the 995 cm- 1 RNA band as a consistent marker across all studied stress conditions, suggesting its potential as a robust biomarker for detecting cells induced into the VBNC state under various stressors.

5'UTR G-quadruplex structure enhances translation in size dependent manner

Translation initiation in bacteria is frequently regulated by various structures in the 5' untranslated region (5'UTR). Previously, we demonstrated that G-quadruplex (G4) formation in non-template DNA enhances transcription. In this study, we aim to explore how G4 formation in mRNA (RG4) at 5'UTR impacts translation using a T7-based in vitro translation system and in E. coli. We show that RG4 strongly promotes translation efficiency in a size-dependent manner. Additionally, inserting a hairpin upstream of the RG4 further enhances translation efficiency, reaching up to a 12-fold increase. We find that the RG4-dependent effect is not due to increased ribosome affinity, ribosome binding site accessibility, or mRNA stability. We propose a physical barrier model in which bulky structures in 5'UTR biases ribosome movement toward the downstream start codon, thereby increasing the translation output. This study provides biophysical insights into the regulatory role of 5'UTR structures in in vitro and bacterial translation, highlighting their potential applications in tuning gene expression.

Assessing the Impacts of Lead Corrosion Control on the Microbial Ecology and Abundance of Drinking-Water-Associated Pathogens in a Full-Scale Drinking Water Distribution System

Increases in phosphate availability in drinking water distribution systems (DWDSs) from the use of phosphate-based corrosion control strategies may result in nutrient and microbial community composition shifts in the DWDS. This study assessed the year-long impacts of full-scale DWDS orthophosphate addition on both the microbial ecology and density of drinking-water-associated pathogens that infect the immunocompromised (DWPIs). Using 16S rRNA gene amplicon sequencing and droplet digital PCR, drinking water microbial community composition and DWPI density were examined. Microbial community composition analysis suggested significant compositional changes after the orthophosphate addition. Significant increases in total bacterial density were observed after orthophosphate addition, likely driven by a 2 log 10 increase in nontuberculous mycobacteria (NTM). Linear effect models confirmed the importance of phosphate addition with phosphorus concentration explaining 17% and 12% of the variance in NTM and L. pneumophila density, respectively. To elucidate the impact of phosphate on NTM aggregation, a comparison of planktonic and aggregate fractions of NTM cultures grown at varying phosphate concentrations was conducted. Aggregation assay results suggested that higher phosphate concentrations cause more disaggregation, and the interaction between phosphate and NTM is species specific. This work reveals new insight into the consequences of orthophosphate application on the DWDS microbiome and highlights the importance of proactively monitoring the DWDS for DWPIs.

Review of the Impact of Biofilm Formation on Recurrent Clostridioides difficile Infection

Clostridioides difficile infection (CDI) may recur in approximately 10-30% of patients, and the risk of recurrence increases with each successive recurrence, reaching up to 65%. C. difficile can form biofilm with approximately 20% of the bacterial genome expressed differently between biofilm and planktonic cells. Biofilm plays several roles that may favor recurrence; for example, it may act as a reservoir of spores, protect the vegetative cells from the activity of antibiotics, and favor the formation of persistent cells. Moreover, the expression of several virulence genes, including TcdA and TcdB toxins, has been associated with recurrence. Several systems and structures associated with adhesion and biofilm formation have been studied in C. difficile, including cell-wall proteins, quorum sensing (including LuxS and Agr), Cyclic di-GMP, type IV pili, and flagella. Most antibiotics recommended for the treatment of CDI do not have activity on spores and do not eliminate biofilm. Therapeutic failure in R-CDI has been associated with the inadequate concentration of drugs in the intestinal tract and the antibiotic resistance of a biofilm. This makes it challenging to eradicate C. difficile in the intestine, complicating antibacterial therapies and allowing non-eliminated spores to remain in the biofilm, increasing the risk of recurrence. In this review, we examine the role of biofilm on recurrence and the challenges of treating CDI when the bacteria form a biofilm.

G. de Lomana A, Gomes-Filho JV, Vêncio RZN, Moritz RL, Koide T, Baliga NS. A Genome-Scale Atlas Reveals Complex Interplay of Transcription and Translation in an Archaeon

The scale of post-transcriptional regulation and the implications of its interplay with other forms of regulation in environmental acclimation are underexplored for organisms of the domain Archaea. Here, we have investigated the scale of post-transcriptional regulation in the extremely halophilic archaeon Halobacterium salinarum NRC-1 by integrating the transcriptome-wide locations of transcript processing sites (TPSs) and SmAP1 binding, the genome-wide locations of antisense RNAs (asRNAs), and the consequences of RNase_2099C knockout on the differential expression of all genes. This integrated analysis has discovered that 54% of all protein-coding genes in the genome of this haloarchaeon are likely targeted by multiple mechanisms for putative post-transcriptional processing and regulation, with about 20% of genes likely being regulated by combinatorial schemes involving SmAP1, asRNAs, and RNase_2099C. Comparative analysis of mRNA levels (transcriptome sequencing [RNA-Seq]) and protein levels (sequential window acquisition of all theoretical fragment ion spectra mass spectrometry [SWATH-MS]) for 2,579 genes over four phases of batch culture growth in complex medium generated additional evidence for the conditional post-transcriptional regulation of 7% of all protein-coding genes. We demonstrate that post-transcriptional regulation may act to fine-tune specialized and rapid acclimation to stressful environments, e.g., as a switch to turn on gas vesicle biogenesis to promote vertical relocation under anoxic conditions and modulate the frequency of transposition by insertion sequence (IS) elements of the IS200/IS605, IS4, and ISH3 families. Findings from this study are provided as an atlas in a public Web resource (https://halodata.systemsbiology.net). IMPORTANCE While the transcriptional regulation landscape of archaea has been extensively investigated, we currently have limited knowledge about post-transcriptional regulation and its driving mechanisms in this domain of life. In this study, we collected and integrated omics data from multiple sources and technologies to infer post-transcriptionally regulated genes and the putative mechanisms modulating their expression at the protein level in Halobacterium salinarum NRC-1. The results suggest that post-transcriptional regulation may drive environmental acclimation by regulating hallmark biological processes. To foster discoveries by other research groups interested in the topic, we extended our integrated data to the public in the form of an interactive atlas (https://halodata.systemsbiology.net).

Genomic insights into the c-di-GMP signaling and biofilm development in the saprophytic spirochete Leptospira biflexa

C-di-GMP is a bacterial second messenger with central role in biofilm formation. Spirochete bacteria from Leptospira genus present a wide diversity, with species of medical importance and environmental species, named as saprophytic. Leptospira form biofilms in the rat's reservoir kidneys and in the environment. Here, we performed genomic analyses to identify enzymatic and effector c-di-GMP proteins in the saprophytic biofilm-forming species Leptospira biflexa serovar Patoc. We identified 40 proteins through local alignments. Amongst them, 16 proteins are potentially functional diguanylate cyclases, phosphodiesterases, or hybrid proteins. We also identified nine effectors, including PilZ proteins. Enrichment analyses suggested that c-di-GMP interacts with cAMP signaling system, CsrA system, and flagella assembly regulation during biofilm development of L. biflexa. Finally, we identified eight proteins in the pathogen Leptospira interrogans serovar Copenhageni that share high similarity with L. biflexa c-di-GMP-related proteins. This work revealed proteins related to c-di-GMP turnover and cellular response in Leptospira and their potential roles during biofilm development.

Matrix is everywhere: extracellular DNA is a link between biofilm and mineralization in Bacillus cereus planktonic lifestyle

To date, the mechanisms of biomineralization induced by bacterial cells in the context of biofilm formation remain the subject of intensive studies. In this study, we analyzed the influence of the medium components on the induction of CaCO₃ precipitation by the Bacillus cereus cells and composition of the extracellular matrix (ECM) formed in the submerged culture. While the accumulation of extracellular polysaccharides and amyloids appeared to be independent of the presence of calcium and urea during the growth, the accumulation of extracellular DNA (eDNA), as well as precipitation of calcium carbonate, required the presence of both ingredients in the medium. Removal of eDNA, which was sensitive to treatment by DNase, did not affect other matrix components but resulted in disruption of cell network formation and a sixfold decrease in the precipitate yield. An experiment with a cell-free system confirmed the acceleration of mineral formation after the addition of exogenous salmon sperm DNA. The observed pathway for the formation of CaCO₃ minerals in B. cereus planktonic culture included a production of exopolysaccharides and negatively charged eDNA lattice promoting local Ca²⁺ supersaturation, which, together with an increase in the concentration of carbonate ions due to pH rise, resulted in the formation of an insoluble precipitate of calcium carbonate. Precipitation of amorphous CaCO₃ on eDNA matrix was followed by crystal formation via the ACC-vaterite-calcite/aragonite pathway and further formation of larger mineral aggregates in complex with extracellular polymeric substances. Taken together, our data showed that DNA in extracellular matrix is an essential factor for triggering the biomineralization in B. cereus planktonic culture.

Selective extracellular secretion of small double-stranded RNA by Tetragenococcus halophilus

Small double-stranded RNAs (dsRNAs) abundantly produced by lactic acid bacteria demonstrate immunomodulatory activity and antiviral protective immunity. However, the extracellular secretion of dsRNA from lactic acid bacteria and their compositional and functional differences compared to the intracellular dsRNA is unknown. In this study, we compared the intracellular and secreted extracellular dsRNA of the lactic acid bacteria, Tetragenococcus halophilus, commonly present in fermented foods, by growing in RNA-free and RNase-free media. We used RNA deep sequencing and in-silico analysis to annotate potential regulatory functions for the comparison. A time series sampling of T. halophilus culture demonstrated growth phase-dependent dynamics in extracellular dsRNA secretion with no major change in the intracellular dsRNA profile. The RNA deep sequencing resulted in thousands of diverse dsRNA fragments with 14-21 nucleotides in size from T. halophilus culture. Over 70% of the secreted extracellular dsRNAs were unique in their sequences compared to the intracellular dsRNAs. Furthermore, the extracellular dsRNA abundantly contains sequences that are not T. halophilus genome encoded, not detected intracellularly and showed higher hits on human transcriptome during in-silico analysis, which suggests the presence of extrachromosomal mobile regulatory elements. Further analysis showed significant enrichment of dsRNA target genes of human transcriptome on cancer pathways and transcription process, indicating the extracellular dsRNA of T. halophilus is different not only at the sequence level but also in function. Studying the bacterial extracellular dsRNA is a promising area of future research, particularly for developing postbiotic fermented functional foods and understanding the impact of commensal gut bacteria on human health.

Multifunctional phototheranostic agent ZnO@Ag for anti-infection through photothermal/photodynamic therapy

To overcome the limitations of traditional therapeutics, nanotechnology offers a synergistic therapeutic approach for the treatment of bacterial infection and biofilms that has attracted attention. Herein, we report on a ZnO@Ag nanocomposite with good biocompatibility synthesized by doping ZnO NPs with silver nanoparticles (Ag NPs). ZnO@Ag nanocomposites were synthesized with varying ratios of Ag NPs (0.5%, 2%, 8%). Under the same experimental conditions, ZnO@8%Ag exhibited outstanding properties compared to the other nanocomposites and the pristine ZnO NPs. ZnO@8%Ag demonstrated excellent photothermal and photodynamic properties. Also, ZnO@8%Ag demonstrated over 99% inhibition of Staphylococcus aureus (S. aureus) under photothermal therapy (PTT) or photodynamics therapy (PDT) as a result of the excessive generation of reactive oxygen species (ROS) by the Ag+ released, while the pristine ZnO showed an insignificant inhibition rate compared to the PBS group (control). Furthermore, ZnO@8%Ag completely disrupted S. aureus biofilm under a combined PTT/PDT treatment, a synergetic trimodal therapy, although the molecular mechanism of biofilm inhibition remains unclear. Hence, the excellent photothermal, photodynamic, biocompatibility, and bactericidal properties of ZnO@8%Ag present it as an appropriate platform for bacterial and biofilm treatment or other biomedically related applications.

Novel prokaryotic system employing previously unknown nucleic acids-based receptors

The present study describes a previously unknown universal system that orchestrates the interaction of bacteria with the environment, named the Teazeled receptor system (TR-system). The identical system was recently discovered within eukaryotes. The system includes DNA- and RNA-based molecules named "TezRs", that form receptor's network located outside the membrane, as well as reverse transcriptases and integrases. TR-system takes part in the control of all major aspects of bacterial behavior, such as intra cellular communication, growth, biofilm formation and dispersal, utilization of nutrients including xenobiotics, virulence, chemo- and magnetoreception, response to external factors (e.g., temperature, UV, light and gas content), mutation events, phage-host interaction, and DNA recombination activity. Additionally, it supervises the function of other receptor-mediated signaling pathways. Importantly, the TR-system is responsible for the formation and maintenance of cell memory to preceding cellular events, as well the ability to "forget" preceding events. Transcriptome and biochemical analysis revealed that the loss of different TezRs instigates significant alterations in gene expression and proteins synthesis.

Antibacterial and antibiofilm activity of Peganum harmala seed extract against multidrug-resistant Pseudomonas aeruginosa pathogenic isolates and molecular mechanism of action

Biofilm formation of the opportunistic pathogen Pseudomonas (P). aeruginosa is one of the major global challenges to control nosocomial infections due to their high resistance to antimicrobials and host defense mechanisms. The present study aimed to assess the antibacterial and the antibiofilm activities of Peganum (P). harmala seed extract against multidrug-resistant P. aeruginosa isolates. Chemical identification of the active compound and determination of its molecular mechanism of action were also investigated. Results showed that P. harmala n-butanol "n-BuOH" extract exhibited antibacterial activity against multidrug-resistant P. aeruginosa isolates. This extract was even more active than conventional antibiotics cefazolin and vaamox when tested against three P. aeruginosa multidrug-resistant isolates. In addition, P. harmala n-BuOH extract exhibited potent bactericidal activity against PAO1 strain at MIC value corresponding to 500 µg/mL and attained 100% killing effect at 24 h of incubation. Furthermore, P. harmala n-BuOH extract showed an antibiofilm activity against P. aeruginosa PAO1 and exhibited 80.43% inhibition at sub-inhibitory concentration. The extract also eradicated 83.99% of the biofilm-forming bacteria. The active compound was identified by gas chromatography-mass spectrometry as an indole alkaloid harmaline. Transcriptomic analysis showed complete inhibition of the biofilm-related gene pilA when PAO1 cells were treated with harmaline. Our results revealed that P. harmala seed extract and its active compound harmaline could be considered as a candidate for a new treatment of multidrug-resistant P. aeruginosa pathogens-associated biofilm infections.

Biofilm formation by strains of Burkholderia cenocepacia lineages IIIA and IIIB and B. gladioli pv. alliicola associated with onion bacterial scale rot

The Burkholderia genus has high ecological and nutritional versatility, having species capable of causing diseases in animals, humans, and plants. During chronic infections in humans, biofilm formation is a characteristic often associated with strains from different species of this genus. However, there is still no information on the formation of biofilms by plant pathogenic strains of B. cenocepacia (Bce) lineages IIIA and IIIB and B. gladioli pv. alliicola (Bga), which are associated with onion bacterial scale rot in the semi-arid region of northeast Brazil. In this study, we performed an in vitro characterization of biofilm formation ability in different culture media by the phytopathogenic strains of Bce and Bga and investigated its relationship with swarming motility. Our results indicated the existence of an intraspecific variation in biofilm formation capacity in vitro by these bacteria and the existence of a negative correlation between swarming motility and biofilm formation for strains of Bce lineage IIIB. In addition, histopathological analyses performed using optical microscopy and scanning electron microscopy revealed the formation of biofilm in vivo by Bce strains in onion tissues.

Insect antimicrobial peptides: potential weapons to counteract the antibiotic resistance

Misuse and overuse of antibiotics have contributed in the last decades to a phenomenon known as antibiotic resistance which is currently considered one of the principal threats to global public health by the World Health Organization. The aim to find alternative drugs has been demonstrated as a real challenge. Thanks to their biodiversity, insects represent the largest class of organisms in the animal kingdom. The humoral immune response includes the production of antimicrobial peptides (AMPs) that are released into the insect hemolymph after microbial infection. In this review, we have focused on insect immune responses, particularly on AMP characteristics, their mechanism of action and applications, especially in the biomedical field. Furthermore, we discuss the Toll, Imd, and JAK-STAT pathways that activate genes encoding for the expression of AMPs. Moreover, we focused on strategies to improve insect peptides stability against proteolytic susceptibility such as D-amino acid substitutions, N-terminus modification, cyclization and dimerization.

New developments in anti-biofilm intervention towards effective management of orthopedic device related infections (ODRI's)

Orthopedic device related infections (ODRI's) represent a difficult to treat situation owing to their biofilm based nature. Biofilm infections once established are difficult to eradicate even with an aggressive treatment regimen due to their recalcitrance towards antibiotics and immune attack. The involvement of antibiotic resistant pathogens as the etiological agent further worsens the overall clinical picture, pressing on the need to look into alternative treatment strategies. The present review highlightes the microbiological challenges associated with treatment of ODRI's due to biofilm formation on the implant surface. Further, it details the newer anti-infective modalities that work either by preventing biofilm formation and/or through effective disruption of the mature biofilms formed on the medical implant. The study, therefore aims to provide a comprehensive insight into the newer anti-biofilm interventions (non-antibiotic approaches) and a better understanding of their mechanism of action essential for improved management of orthopedic implant infections.

Mechanisms of Tolerance and Resistance to Chlorhexidine in Clinical Strains of Klebsiella pneumoniae Producers of Carbapenemase: Role of New Type II Toxin-Antitoxin System, PemIK

Although the failure of antibiotic treatment is normally attributed to resistance, tolerance and persistence display a significant role in the lack of response to antibiotics. Due to the fact that several nosocomial pathogens show a high level of tolerance and/or resistance to chlorhexidine, in this study we analyzed the molecular mechanisms associated with chlorhexidine adaptation in two clinical strains of Klebsiella pneumoniae by phenotypic and transcriptomic studies. These two strains belong to ST258-KPC3 (high-risk clone carrying β-lactamase KPC3) and ST846-OXA48 (low-risk clone carrying β-lactamase OXA48). Our results showed that the K. pneumoniae ST258-KPC3CA and ST846-OXA48CA strains exhibited a different behavior under chlorhexidine (CHLX) pressure, adapting to this biocide through resistance and tolerance mechanisms, respectively. Furthermore, the appearance of cross-resistance to colistin was observed in the ST846-OXA48CA strain (tolerant to CHLX), using the broth microdilution method. Interestingly, this ST846-OXA48CA isolate contained a plasmid that encodes a novel type II toxin/antitoxin (TA) system, PemI/PemK. We characterized this PemI/PemK TA system by cloning both genes into the IPTG-inducible pCA24N plasmid, and found their role in persistence and biofilm formation. Accordingly, the ST846-OXA48CA strain showed a persistence biphasic curve in the presence of a chlorhexidine-imipenem combination, and these results were confirmed by the enzymatic assay (WST-1).

Ferulic Acid Inactivates Shigella flexneri through Cell Membrane Destructieon, Biofilm Retardation, and Altered Gene Expression

Antibiotic resistance and capacity for biofilm formation of Shigella flexneri render previous prevention and control strategies minimally effective. Ferulic acid (FA) has been demonstrated to be useful due to its application in foods as an alternative natural preservative. However, information regarding the S. flexneri phenotype and molecular responses to FA exposure is limited. The present study investigated the effects of FA on S. flexneri planktonic growth and biofilm formation. The results demonstrated that the cell membrane of S. flexneri in planktonic growth mode exhibited irreversible destruction after FA exposure, as characterized by decreased cell viability, leakage of cytoplasmic constituents, accelerated adenosine triphosphate (ATP) consumption, cell membrane depolarization, and cellular morphological changes. FA significantly inhibited S. flexneri adhesion and biofilm formation at a working concentration (1/8 MIC) that almost did not inhibit planktonic growth. Transcriptomics profiling showed that the exposure to a subinhibitory concentration of FA dramatically altered gene expression in the S. flexneri biofilm, as a total of 169 differentially expressed genes (DEGs) were upregulated and 533 DEGs were downregulated, compared to the intact biofilm. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis showed that the DEGs were mainly involved in pathways of ribosomes, ABC transporters, and the citrate cycle. Furthermore, we show that FA altered the transcription of S. flexneri genes associated with adhesion, transcriptional regulation, and the synthesis and transport of extracellular polymeric substances that contribute to biofilm formation. These data provide novel insights into S. flexneri behavioral responses to FA exposure and suggest that FA could effectively constrain S. flexneri and its biofilm formation.

Transcriptional and Mycolic Acid Profiling in Mycobacterium bovis BCG In Vitro Show an Effect for c-di-GMP and Overlap between Dormancy and Biofilms

Mycobacterium tuberculosis produces mycolic acids which are relevant for persistence, recalcitrance to antibiotics and defiance to host immunity. c-di-GMP is a second messenger involved in transition from planktonic cells to biofilms, whose levels are controlled by diguanylate cyclases (DGC) and phosphodiesterases (PDE). The transcriptional regulator dosR, is involved in response to low oxygen, a condition likely happening to a subset of cells within biofilms. Here, we found that in M. bovis BCG, expression of both BCG1416c and BCG1419c genes, which code for a DGC and a PDE, respectively, decreased in both stationary phase and during biofilm production. The kasA, kasB, and fas genes, which are involved in mycolic acid biosynthesis, were induced in biofilm cultures, as was dosR, therefore suggesting an inverse correlation in their expression compared with that of genes involved in c-di-GMP metabolism. The relative abundance within trehalose dimycolate (TDM) of α-mycolates decreased during biofilm maturation, with methoxy mycolates increasing over time, and keto species remaining practically stable. Moreover, addition of synthetic c-di-GMP to mid-log phase BCG cultures reduced methoxy mycolates, increased keto species and practically did not affect α-mycolates, showing a differential effect of c-di-GMP on keto- and methoxy-mycolic acid metabolism.

Bacterial biopolymers: from pathogenesis to advanced materials

Bacteria are prime cell factories that can efficiently convert carbon and nitrogen sources into a large diversity of intracellular and extracellular biopolymers, such as polysaccharides, polyamides, polyesters, polyphosphates, extracellular DNA and proteinaceous components. Bacterial polymers have important roles in pathogenicity, and their varied chemical and material properties make them suitable for medical and industrial applications. The same biopolymers when produced by pathogenic bacteria function as major virulence factors, whereas when they are produced by non-pathogenic bacteria, they become food ingredients or biomaterials. Interdisciplinary research has shed light on the molecular mechanisms of bacterial polymer synthesis, identified new targets for antibacterial drugs and informed synthetic biology approaches to design and manufacture innovative materials. This Review summarizes the role of bacterial polymers in pathogenesis, their synthesis and their material properties as well as approaches to design cell factories for production of tailor-made bio-based materials suitable for high-value applications.

Monitoring Biofilm Formation and Microbial Interactions that May Occur During a Salmonella Contamination Incident across the Network of a Water Bottling Plant

The present study aims to monitor the ability of Salmonella to colonize and compete as a member of the mixed species biofilm within key points at a water bottling plant, in case of a contamination incident with this major foodborne pathogen. To achieve this goal, bacterial communities throughout the production line were collected and their identities were investigated by microbial counts and polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). These bacterial communities alone or along with constructed Salmonella enterica serovar Typhimurium (ST) fluorescence-based bioreporters were left to form a biofilm on stainless steel for 6 days at 20 °C. ST bioreporters were constructed by introducing plasmids expressing EYFP (enhanced yellow fluorescent protein) fusions of the genes csgB, csrA, sspH2, and fliD into ST 14028S. The bead vortexing-plate counting method was applied for the enumeration of the biofilm population, while the behavior of the bioreporters was evaluated by fluorescence microscopy. From a set of 16 samples that were collected from the plant, species of Citrobacter, Staphylococcus, Pseudomonas, Bacillus, and Exiguobacterium were identified. The presence of these indigenous bacteria neither inhibited nor enhanced the biofilm formation of ST in mixed bacterial communities (p > 0.05). Furthermore, the csrA-based bioreporter was shown to be induced in multispecies biofilms with Citrobacter. In conclusion, this study enhanced our knowledge of bacterial interactions occurring within a biofilm in a water bottling plant.

Liquid-Infused Structured Titanium Surfaces: Antiadhesive Mechanism to Repel Streptococcus oralis Biofilms

To combat implant-associated infections, there is a need for novel materials which effectively inhibit bacterial biofilm formation. In the present study, the antiadhesive properties of titanium surface functionalization based on the "slippery liquid-infused porous surfaces" (SLIPS) principle were demonstrated and the underlying mechanism was analyzed. The immobilized liquid layer was stable over 13 days of continuous flow in an oral flow chamber system. With increasing flow rates, the surface exhibited a significant reduction in attached biofilm of both the oral initial colonizer  Streptococcus oralis and an oral multispecies biofilm composed of S. oralis, Actinomyces naeslundii, Veillonella dispar, and Porphyromonas gingivalis. Using single cell force spectroscopy, reduced S. oralis adhesion forces on the lubricant layer could be measured. Gene expression patterns in biofilms on SLIPS, on control surfaces, and expression patterns of planktonic cultures were also compared. For this purpose, the genome of S. oralis strain ATCC 9811 was sequenced using PacBio Sequel technology. Even though biofilm cells showed clear changes in gene expression compared to planktonic cells, no differences could be detected between bacteria on SLIPS and on control surfaces. Therefore, it can be concluded that the ability of liquid-infused titanium to repel S. oralis biofilms is mainly due to weakened bacterial adhesion to the underlying liquid interface.

Marano M, Vojnov AA. The histone-like protein HupB influences biofilm formation and virulence in Xanthomonas citri ssp. citri through the regulation of flagellar biosynthesis

Citrus canker is an important disease of citrus, whose causal agent is the bacterium Xanthomonas citri ssp. citri (Xcc). In previous studies, we found a group of Xcc mutants, generated by the insertion of the Tn5 transposon, which showed impaired ability to attach to an abiotic substrate. One of these mutants carries the Tn5 insertion in hupB, a gene encoding a bacterial histone-like protein, homologue to the β-subunit of the Heat-Unstable (HU) nucleoid protein of Escherichia coli. These types of protein are necessary to maintain the bacterial nucleoid organization and the global regulation of gene expression. Here, we characterized the influence of the mutation in hupB regarding Xcc biofilm formation and virulence. The mutant strain hupB was incapable of swimming in soft agar, whereas its complemented strain partially recovered this phenotype. Electron microscope imaging revealed that impaired motility of hupB was a consequence of the absence of the flagellum. Comparison of the expression of flagellar genes between the wild-type strain and hupB showed that the mutant exhibited decreased expression of fliC (encoding flagellin). The hupB mutant also displayed reduced virulence compared with the wild-type strain when they were used to infect Citrus lemon plants using different infection methods. Our results therefore show that the histone-like protein HupB plays an essential role in the pathogenesis of Xcc through the regulation of biofilm formation and biosynthesis of the flagellum.

Nanocomposite of Ag-Doped ZnO and AgO Nanocrystals as a Preventive Measure to Control Biofilm Formation in Eggshell and Salmonella spp. Entry Into Eggs

Salmonella spp. is an important foodborne agent of salmonellosis, whose sources in humans often include products of avian origin. The control of this bacterium is difficult especially when Salmonella spp. is organized into biofilms. We hypothesized that the novel nanocomposites of ZnO nanocrystals doped with silver (Ag) and silver oxide (AgO) nanocrystals (ZnO:Ag-AgO) synthesized by the coprecipitation method could control or prevent the formation of Salmonella Enteritidis (SE) and Salmonella Heidelberg (SH) biofilm and its entry into turkey eggs. The diffraction characteristics of ZnO and AgO showed sizes of 28 and 30 nm, respectively. The Zn to Ag substitution into the ZnO crystalline structure was evidenced by the ionic radius of Ag+2 (1.26 Å), which is greater than Zn+2 (0.74 Å). For the SE analyses post-biofilm formation, the ZnO:Ag-AgO was not able to eliminate the biofilm, but the bacterial load was lower than that of the control group. Additionally, SE was able to infiltrate into the eggs and was found in both albumen and yolk. For the SH analyses applied onto the eggshells before biofilm formation, the ZnO:Ag-AgO treatment prevented biofilm formation, and although the bacterium infiltration into the eggs was observed in all treated groups, it was significantly smaller in ZnO:Ag-AgO pre-treated eggs, and SH could not reach the yolk. There was no difference in pore size between groups; therefore, the inhibition of biofilm formation and the prevention of bacterium entry into the egg were attributable to the use of ZnO:Ag-AgO, which was not influenced by the egg structure. Although the amount of Ag and Zn in the shell of the ZnO:Ag-AgO group was greater in relation to the control, this difference was not detected in the other egg components. In the search for new measures that are effective, safe and viable for controlling microorganisms in poultry farming, the application of a nanocomposite of Ag-doped ZnO and AgO nanocrystals appears as an alternative of great potential to prevent Salmonella sp biofilms in eggshells and other surfaces.

Structure and predictive functional profiling of microbial communities in two biotrickling filters treated with continuous/discontinuous waste gases

Two biotrickling filters were operated in continuous (BTF1) and discontinuous (BTF2) modes at a constant empty bed residence time of 60 s for 60 days. From day 60, the operation mode of each BTF was oppositely switched. Higher removal efficiencies of five aromatic pollutants were recorded with BTF1 (> 77.2%). The switch in the operation mode did not alter the removal performance of BTF1. Comparatively, BTF2 was not successfully acclimated in the discontinuous operation mode. Once the mode had been switched to continuous mode, the removal efficiencies of BTF2 on all pollutants increased drastically and finally exceeded the values observed in BTF1, with the single exception of p-xylene. Principle coordinate analysis and analysis of similarities (ANOSIM) showed that the structure of the microbial communities differed considerably between both BTFs (R = 1.000, p < 0.01) as well as before and after the switch in BTF2 (R = 0.996, p < 0.01). The random forest model demonstrated that Mycobacterium, Burkholderia, and Comamonas were the three most important bacterial genera contributing to the differences in microbial communities between the two BTFs. Metagenomics inferred by PICUSt (phylogenetic investigation of communities by reconstruction of unobserved states) indicated that BTF2 had high degradation potential for aromatic pollutants, although those genes involved in biofilm formation were less active in BTF2 than those in BTF1.

A Systematic Overview of Type II and III Toxin-Antitoxin Systems with a Focus on Druggability

Toxin-antitoxin (TA) systems are known to play various roles in physiological processes, such as gene regulation, growth arrest and survival, in bacteria exposed to environmental stress. Type II TA systems comprise natural complexes consisting of protein toxins and antitoxins. Each toxin and antitoxin participates in distinct regulatory mechanisms depending on the type of TA system. Recently, peptides designed by mimicking the interfaces between TA complexes showed its potential to activate the activity of toxin by competing its binding counterparts. Type II TA systems occur more often in pathogenic bacteria than in their nonpathogenic kin. Therefore, they can be possible drug targets, because of their high abundance in some pathogenic bacteria, such as Mycobacterium tuberculosis. In addition, recent bioinformatic analyses have shown that type III TA systems are highly abundant in the intestinal microbiota, and recent clinical studies have shown that the intestinal microbiota is linked to inflammatory diseases, obesity and even several types of cancer. We therefore focused on exploring the putative relationship between intestinal microbiota-related human diseases and type III TA systems. In this paper, we review and discuss the development of possible druggable materials based on the mechanism of type II and type III TA system.

Global assessment of small RNAs reveals a non-coding transcript involved in biofilm formation and attachment in Acinetobacter baumannii ATCC 17978

Many strains of Acinetobacter baumannii have been described as being able to form biofilm. Small non-coding RNAs (sRNAs) control gene expression in many regulatory circuits in bacteria. The aim of the present work was to provide a global description of the sRNAs produced both by planktonic and biofilm-associated (sessile) cells of A. baumannii ATCC 17978, and to compare the corresponding gene expression profiles to identify sRNAs molecules associated to biofilm formation and virulence. sRNA was extracted from both planktonic and sessile cells and reverse transcribed. cDNA was subjected to 454-pyrosequencing using the GS-FLX Titanium chemistry. The global analysis of the small RNA transcriptome revealed different sRNA expression patterns in planktonic and biofilm associated cells, with some of the transcripts only expressed or repressed in sessile bacteria. A total of 255 sRNAs were detected, with 185 of them differentially expressed in the different types of cells. A total of 9 sRNAs were expressed only in biofilm cells, while the expression of other 21 coding regions were repressed only in biofilm cells. Strikingly, the expression level of the sRNA 13573 was 120 times higher in biofilms than in planktonic cells, an observation that prompted us to further investigate the biological role of this non-coding transcript. Analyses of an isogenic mutant and over-expressing strains revealed that the sRNA 13573 gene is involved in biofilm formation and attachment to A549 human alveolar epithelial cells. The present work serves as a basis for future studies examining the complex regulatory network that regulate biofilm biogenesis and attachment to eukaryotic cells in A. baumannii ATCC 17978.

Spatial Organization Plasticity as an Adaptive Driver of Surface Microbial Communities

Biofilms are dynamic habitats which constantly evolve in response to environmental fluctuations and thereby constitute remarkable survival strategies for microorganisms. The modulation of biofilm functional properties is largely governed by the active remodeling of their three-dimensional structure and involves an arsenal of microbial self-produced components and interconnected mechanisms. The production of matrix components, the spatial reorganization of ecological interactions, the generation of physiological heterogeneity, the regulation of motility, the production of actives enzymes are for instance some of the processes enabling such spatial organization plasticity. In this contribution, we discussed the foundations of architectural plasticity as an adaptive driver of biofilms through the review of the different microbial strategies involved. Moreover, the possibility to harness such characteristics to sculpt biofilm structure as an attractive approach to control their functional properties, whether beneficial or deleterious, is also discussed.

A starvation-induced regulator, RovM, acts as a switch for planktonic/biofilm state transition in Yersinia pseudotuberculosis

The transition between the planktonic state and the biofilm-associated state is a key developmental decision for pathogenic bacteria. Biofilm formation by Yersinia pestis is regulated by hmsHFRS genes (β-1, 6-N-acetyl-D-glucosamine synthesis operon) in its flea vector and in vitro. However, the mechanism of biofilm formation in Yersinia pseudotuberculosis remains elusive. In this study, we demonstrate that the LysR-type regulator RovM inversely regulates biofilm formation and motility in Y. pseudotuberculosis by acting as a transcriptional regulator of these two functions. RovM is strongly induced during growth in minimal media but strongly repressed in complex media. On one hand, RovM enhances bacterial motility by activating the expression of FlhDC, the master regulator of flagellar genes, via the recognition of an operator upstream of the flhDC promoter. On the other hand, RovM represses β-GlcNAc production under nutrition-limited conditions, negatively regulating hmsHFRS expression by directly binding to the -35 element of its promoter. Compared to wild-type bacteria, the rovM mutant established denser biofilms and caused more extensive mortality in mice and silkworm larvae. These results indicate that RovM acts as a molecular switch to coordinate the expression of genes involved in biofilm formation and motility in response to the availability of nutrients.

Zinc oxide nanoparticle reduced biofilm formation and antigen 43 expressions in uropathogenic Escherichiacoli

OBJECTIVES

This study aimed to investigate the effect of zinc oxide nanoparticles (ZnO-np) on biofilm formation and expression of the flu gene in uropathogenic Escherichia coli (UPEC) strains.

MATERIALS AND METHODS

Minimum inhibitory concentration (MIC) of ZnO-np was determined by agar dilution method. The effect of MIC and sub-MIC concentrations of ZnO-np on biofilm formation were determined by microtiter plate assay. The expression level of the flu gene was assessed by Real-Time PCR assay.

RESULTS

MIC and sub-MIC ZnO-np concentrations reduced biofilm formation by 50% and 33.4%, respectively. Sub-MIC ZnO-np concentration significantly reduced the flu gene expression in the UPEC isolates (P<0.0001).

CONCLUSION

The sub-MIC concentration of ZnO-np reduces biofilm formation and flu gene expression in UPEC isolates. It is suggested to use nanoparticles for coating medical devices to prevent bacterial colonization.

Rifampicin-Resistance Mutations in the rpoB Gene in Bacillus velezensis CC09 have Pleiotropic Effects

Rifampicin resistance (Rif^r) mutations in the RNA polymerase β subunit (rpoB) gene exhibit pleiotropic phenotypes as a result of their effects on the transcription machinery in prokaryotes. However, the differences in the effects of the mutations on the physiology and metabolism of the bacteria remain unknown. In this study, we isolated seven Rif^r mutations in rpoB, including six single point mutations (H485Y, H485C, H485D, H485R, Q472R, and S490L) and one double point mutation (S490L/S617F) from vegetative cells of an endophytic strain, Bacillus velezensis CC09. Compared to the wild-type (WT) strain (CC09), the H485R and H485D mutants exhibited a higher degree of inhibition of Aspergillus niger spore germination, while the H485Y, S490L, Q472R, and S490L/S617F mutants exhibited a lower degree of inhibition due to their lower production of the antibiotic iturin A. These mutants all exhibited defective phenotypes in terms of pellicle formation, sporulation, and swarming motility. A hierarchical clustering analysis of the observed phenotypes indicated that the four mutations involving amino acid substitutions at H485 in RpoB belonged to the same cluster. In contrast, the S490L and Q472R mutations, as well as the WT strain, were in another cluster, indicating a functional connection between the mutations in B. velezensis and phenotypic changes. Our data suggest that Rif^r mutations cannot only be used to study transcriptional regulation mechanisms, but can also serve as a tool to increase the production of bioactive metabolites in B. velezensis.

Comparison of biofilm formation and motility processes in arsenic-resistant Thiomonas spp. strains revealed divergent response to arsenite

Bacteria of the genus Thiomonas are found ubiquitously in arsenic contaminated waters such as acid mine drainage (AMD), where they contribute to the precipitation and the natural bioremediation of arsenic. In these environments, these bacteria have developed a large range of resistance strategies among which the capacity to form particular biofilm structures. The biofilm formation is one of the most ubiquitous adaptive response observed in prokaryotes to various stresses, such as those induced in the presence of toxic compounds. This study focused on the process of biofilm formation in three Thiomonas strains (CB1, CB2 and CB3) isolated from the same AMD. The results obtained here show that these bacteria are all capable of forming biofilms, but the architecture and the kinetics of formation of these biofilms differ depending on whether arsenite is present in the environment and from one strain to another. Indeed, two strains favoured biofilm formation, whereas one favoured motility in the presence of arsenite. To identify the underlying mechanisms, the patterns of expression of some genes possibly involved in the process of biofilm formation were investigated in Thiomonas sp. CB2 in the presence and absence of arsenite, using a transcriptomic approach (RNA‐seq). The findings obtained here shed interesting light on how the formation of biofilms, and the motility processes contribute to the adaptation of Thiomonas strains to extreme environments.

In vitro Determination of Extracellular Proteins from Xylella fastidiosa

The phytopathogen Xylella fastidiosa causes economic losses in important agricultural crops. Xylem vessel occlusion caused by biofilm formation is the major mechanism underlying the pathogenicity of distinct strains of X. fastidiosa. Here, we provide a detailed in vitro characterization of the extracellular proteins of X. fastidiosa. Based on the results, we performed a comparison with a strain J1a12, which cannot induce citrus variegated chlorosis symptoms when inoculated into citrus plants. We then extend this approach to analyze the extracellular proteins of X. fastidiosa in media supplemented with calcium. We verified increases in extracellular proteins concomitant with the days of growth and, consequently, biofilm development (3-30 days). Outer membrane vesicles carrying toxins were identified beginning at 10 days of growth in the 9a5c strain. In addition, a decrease in extracellular proteins in media supplemented with calcium was observed in both strains. Using mass spectrometry, 71 different proteins were identified during 30 days of X. fastidiosa biofilm development, including proteases, quorum-sensing proteins, biofilm formation proteins, hypothetical proteins, phage-related proteins, chaperones, toxins, antitoxins, and extracellular vesicle membrane components.

Understanding the Streptococcus mutans Cid/Lrg System through CidB Function

The Streptococcus mutans lrgAB and cidAB operons have been previously described as a potential model system to dissect the complexity of biofilm development and virulence of S. mutans Herein, we have attempted to further characterize the Cid/Lrg system by focusing on CidB, which has been shown to be critical for the ability of S. mutans to survive and persist in a nonpreferred oxygen-enriched condition. We have found that the expression level of cidB is critical to oxidative stress tolerance of S. mutans, most likely by impacting lrg expression. Intriguingly, the impaired aerobic growth phenotype of the cidB mutant could be restored by the additional loss of either CidA or LrgA. Growth-dependent expression of cid and lrg was demonstrated to be tightly under the control of both CcpA and the VicKR two-component system (TCS), regulators known to play an essential role in controlling major catabolic pathways and cell envelope homeostasis, respectively. RNA sequencing (RNA-Seq) analysis revealed that mutation of cidB resulted in global gene expression changes, comprising major domains of central metabolism and virulence processes, particularly in those involved with oxidative stress resistance. Loss of CidB also significantly changed the expression of genes related to genomic islands (GI) TnSmu1 and TnSmu2, the CRISPR (clustered regularly interspaced short palindromic repeats)-Cas system, and toxin-antitoxin (T/A) modules. Taken together, these data show that CidB impinges on the stress response, as well as the fundamental cellular physiology of S. mutans, and further suggest a potential link between Cid/Lrg-mediated cellular processes, S. mutans pathogenicity, and possible programmed growth arrest and cell death mechanisms.

IMPORTANCE

The ability of Streptococcus mutans to survive a variety of harmful or stressful conditions and to emerge as a numerically significant member of stable oral biofilm communities are essential elements for its persistence and cariogenicity. In this study, the homologous cidAB and lrgAB operons, previously identified as being highly balanced and coordinated during S. mutans aerobic growth, were further characterized through the functional and transcriptomic analysis of CidB. Precise control of CidB levels is shown to impact the expression of lrg, oxidative stress tolerance, major metabolic domains, and the molecular modules linked to cell death and lysis. This study advances our understanding of the Cid/Lrg system as a key player in the integration of complex environmental signals (such as oxidative stress) into the regulatory networks that modulate S. mutans virulence and cell homeostasis.

Emerging Roles of Toxin-Antitoxin Modules in Bacterial Pathogenesis

Toxin-antitoxin (TA) cassettes are encoded widely by bacteria. The modules typically comprise a protein toxin and protein or RNA antitoxin that sequesters the toxin factor. Toxin activation in response to environmental cues or other stresses promotes a dampening of metabolism, most notably protein translation, which permits survival until conditions improve. Emerging evidence also implicates TAs in bacterial pathogenicity. Bacterial persistence involves entry into a transient semi-dormant state in which cells survive unfavorable conditions including killing by antibiotics, which is a significant clinical problem. TA complexes play a fundamental role in inducing persistence by downregulating cellular metabolism. Bacterial biofilms are important in numerous chronic inflammatory and infectious diseases and cause serious therapeutic problems due to their multidrug tolerance and resistance to host immune system actions. Multiple TAs influence biofilm formation through a network of interactions with other factors that mediate biofilm production and maintenance. Moreover, in view of their emerging contributions to bacterial virulence, TAs are potential targets for novel prophylactic and therapeutic approaches that are required urgently in an era of expanding antibiotic resistance. This review summarizes the emerging evidence that implicates TAs in the virulence profiles of a diverse range of key bacterial pathogens that trigger serious human disease.

Microbial Surface Colonization and Biofilm Development in Marine Environments

Biotic and abiotic surfaces in marine waters are rapidly colonized by microorganisms. Surface colonization and subsequent biofilm formation and development provide numerous advantages to these organisms and support critical ecological and biogeochemical functions in the changing marine environment. Microbial surface association also contributes to deleterious effects such as biofouling, biocorrosion, and the persistence and transmission of harmful or pathogenic microorganisms and their genetic determinants. The processes and mechanisms of colonization as well as key players among the surface-associated microbiota have been studied for several decades. Accumulating evidence indicates that specific cell-surface, cell-cell, and interpopulation interactions shape the composition, structure, spatiotemporal dynamics, and functions of surface-associated microbial communities. Several key microbial processes and mechanisms, including (i) surface, population, and community sensing and signaling, (ii) intraspecies and interspecies communication and interaction, and (iii) the regulatory balance between cooperation and competition, have been identified as critical for the microbial surface association lifestyle. In this review, recent progress in the study of marine microbial surface colonization and biofilm development is synthesized and discussed. Major gaps in our knowledge remain. We pose questions for targeted investigation of surface-specific community-level microbial features, answers to which would advance our understanding of surface-associated microbial community ecology and the biogeochemical functions of these communities at levels from molecular mechanistic details through systems biological integration.

General Overview on Nontuberculous Mycobacteria, Biofilms, and Human Infection

Nontuberculous mycobacteria (NTM) are emergent pathogens whose importance in human health has been growing. After being regarded mainly as etiological agents of opportunist infections in HIV patients, they have also been recognized as etiological agents of several infections on immune-competent individuals and healthcare-associated infections. The environmental nature of NTM and their ability to assemble biofilms on different surfaces play a key role in their pathogenesis. Here, we review the clinical manifestations attributed to NTM giving particular importance to the role played by biofilm assembly.

Archaeal type IV pili and their involvement in biofilm formation

Type IV pili are ancient proteinaceous structures present on the cell surface of species in nearly all bacterial and archaeal phyla. These filaments, which are required for a diverse array of important cellular processes, are assembled employing a conserved set of core components. While type IV pilins, the structural subunits of pili, share little sequence homology, their signal peptides are structurally conserved allowing for in silico prediction. Recently, in vivo studies in model archaea representing the euryarchaeal and crenarchaeal kingdoms confirmed that several of these pilins are incorporated into type IV adhesion pili. In addition to facilitating surface adhesion, these in vivo studies also showed that several predicted pilins are required for additional functions that are critical to biofilm formation. Examples include the subunits of Sulfolobus acidocaldarius Ups pili, which are induced by exposure to UV light and promote cell aggregation and conjugation, and a subset of the Haloferax volcanii adhesion pilins, which play a critical role in microcolony formation while other pilins inhibit this process. The recent discovery of novel pilin functions such as the ability of haloarchaeal adhesion pilins to regulate swimming motility may point to novel regulatory pathways conserved across prokaryotic domains. In this review, we will discuss recent advances in our understanding of the functional roles played by archaeal type IV adhesion pili and their subunits, with particular emphasis on their involvement in biofilm formation.

Scratching the surface - tobacco-induced bacterial biofilms

Individual environmental factors, such as iron, temperature and oxygen, are known to have a profound effect on bacterial phenotype. Therefore, it is surprising so little known is about the influence of chemically complex cigarette smoke on bacterial physiology. Recent evidence has demonstrated that tobacco smoke and components alter the bacterial surface and promote biofilm formation in several important human pathogens, including Staphylococcus aureus, Streptococcus mutans, Klebsiella pneumonia, Porphyromonas gingivalis and Pseudomonas aeruginosa. The mechanisms underlying this phenomenon and the relevance to increased susceptibility to infectious disease in smokers and to treatment are reviewed.

Non-coding RNA regulation in pathogenic bacteria located inside eukaryotic cells

Intracellular bacterial pathogens have evolved distinct lifestyles inside eukaryotic cells. Some pathogens coexist with the infected cell in an obligate intracellular state, whereas others transit between the extracellular and intracellular environment. Adaptation to these intracellular lifestyles is regulated in both space and time. Non-coding small RNAs (sRNAs) are post-transcriptional regulatory molecules that fine-tune important processes in bacterial physiology including cell envelope architecture, intermediate metabolism, bacterial communication, biofilm formation, and virulence. Recent studies have shown production of defined sRNA species by intracellular bacteria located inside eukaryotic cells. The molecules targeted by these sRNAs and their expression dynamics along the intracellular infection cycle remain, however, poorly characterized. Technical difficulties linked to the isolation of “intact” intracellular bacteria from infected host cells might explain why sRNA regulation in these specialized pathogens is still a largely unexplored field. Transition from the extracellular to the intracellular lifestyle provides an ideal scenario in which regulatory sRNAs are intended to participate; so much work must be done in this direction. This review focuses on sRNAs expressed by intracellular bacterial pathogens during the infection of eukaryotic cells, strategies used with these pathogens to identify sRNAs required for virulence, and the experimental technical challenges associated to this type of studies. We also discuss varied techniques for their potential application to study RNA regulation in intracellular bacterial infections.

Effect of algae and plant lectins on planktonic growth and biofilm formation in clinically relevant bacteria and yeasts

This study aimed to evaluate the abilities of plant and algae lectins to inhibit planktonic growth and biofilm formation in bacteria and yeasts. Initially, ten lectins were tested on Staphylococcus epidermidis, Staphylococcus aureus, Klebsiella oxytoca, Pseudomonas aeruginosa, Candida albicans, and C. tropicalis at concentrations of 31.25 to 250 μg/mL. The lectins from Cratylia floribunda (CFL), Vatairea macrocarpa (VML), Bauhinia bauhinioides (BBL), Bryothamnion seaforthii (BSL), and Hypnea musciformis (HML) showed activities against at least one microorganism. Biofilm formation in the presence of the lectins was also evaluated; after 24 h of incubation with the lectins, the biofilms were analyzed by quantifying the biomass (by crystal violet staining) and by enumerating the viable cells (colony-forming units). The lectins reduced the biofilm biomass and/or the number of viable cells to differing degrees depending on the microorganism tested, demonstrating the different characteristics of the lectins. These findings indicate that the lectins tested in this study may be natural alternative antimicrobial agents; however, further studies are required to better elucidate the functional use of these proteins.