Biocontrol treatment: Application of Bdellovibrio bacteriovorus HD100 against burn wound infection caused by Pseudomonas aeroginosa in mice.

Owing to the high level of resistance to various antibiotics in bacteria causing burn wound infections, the alternative therapeutics is highly demanded. Bdellovibrio and like organisms (BALOs) seem to be a superb choice. In the present study, Bdellovibrio bacteriovorus HD100 was selected for treating burn wound infection caused by Pseudomonas aeruginosa strain PAO1 in a mouse model. In this experiment, two treatments, meropenem as antibiotic and B. bacteriovorus, were employed. Histopathology indicated an accelerated healing rate in both treatments in comparison with the control. Moreover, quantitative reverse transcription PCR (qRT-PCR) was applied to investigate the expression of tnf-α (tumor necrosis factor alpha), pdgf (platelet-derived growth factor), tgf-ß1 (transforming growth factor beta1), ifn-γ (interferon gamma), vegf (vascular endothelial group factor), and col1 (collagen type 1). The results demonstrated that treating burn wound areas with Bdellovibrio not only decrease the inflammatory phase period, but also may improve the characteristics of proliferative phases of wound healing. In addition, a significant difference was explored between the two treatment groups in the regulation of all genes, except for pdgf revealed a significant up regulation in both treatment groups. The results disclose that Bdellovibrio attenuates P. aeruginosa in burn wounds infections and improves the wound healing process.

Strain-specific predation of Bdellovibrio bacteriovorus on Pseudomonas aeruginosa with a higher range for cystic fibrosis than for bacteremia isolates.

This work aimed to evaluate the predatory activity of Bdellovibrio bacteriovorus 109J on clinical isolates of Pseudomonas aeruginosa selected from well-characterized collections of cystic fibrosis (CF) lung colonization (n = 30) and bloodstream infections (BSI) (n = 48) including strains selected by genetic lineage (frequent and rare sequence types), antibiotic resistance phenotype (susceptible and multidrug-resistant isolates), and colony phenotype (mucoid and non-mucoid isolates). The intraspecies predation range (I-PR) was defined as the proportion of susceptible strains within the entire collection. In contrast, the predation efficiency (PE) is the ratio of viable prey cells remaining after predation compared to the initial inoculum. I-PR was significantly higher for CF (67%) than for BSI P. aeruginosa isolates (35%) probably related to an environmental origin of CF strains whereas invasive strains are more adapted to humans. I-PR correlation with bacterial features such as mucoid morphotype, genetic background, or antibiotic susceptibility profile was not detected. To test the possibility of increasing I-PR of BSI isolates, a polyhydroxyalkanoate depolymerase deficient B. bacteriovorus bd2637 mutant was used. Global median I-PR and PE values remained constant for both predators, but 31.2% of 109J-resistant isolates were susceptible to the mutant, and 22.9% of 109J-susceptible isolates showed resistance to predation by the mutant, pointing to a predator-prey specificity process. The potential use of predators in the clinical setting should be based on the determination of the I-PR for each species, and the PE of each particular target strain.

Structural and functional characterization of a maltose/maltodextrin ABC transporter comprising a single solute binding domain (MalE) fused to the transmembrane subunit MalF.

Canonical ATP-binding cassette import systems rely on extracellular substrate binding proteins (SBP) for function. In gram-negative bacteria, SBPs are usually freely diffusible in the periplasm and, where studied, exist in excess over their cognate transporters. However, in vitro studies with the maltose transporter of Escherichia coli (MalFGK2) have demonstrated that mechanistically one copy of its SBP (MalE) per transport complex is sufficient for activity. To address whether such a condition is physiologically relevant, we have characterized a homolog of the E. coli system from the gram-negative bacterium Bdellovibrio bacteriovorus which has a single copy of a maltose binding domain fused to the MalF subunit. Both transporters share substrate specificity for maltose and linear maltodextrins. Specific ATPase and transport activities of the B. bacteriovorus transporter were comparable to those of the E. coli system assayed at a 1:1 M ratio of MalE to the transport complex. While MalEEc was able to additionally increase ATPase activity of MalFGK2Bb, the isolated MalE domain of B. bacteriovorus failed to stimulate the E. coli system. Strikingly, interactions of the MalE domain with the transmembrane subunits during the transport cycle as studied by site-specific cross-linking were found to differ from those observed for E. coli MalE-FGK2.

Individual Patterns of Complexity in Cystic Fibrosis Lung Microbiota, Including Predator Bacteria, over a 1-Year Period.

Cystic fibrosis (CF) lung microbiota composition has recently been redefined by the application of next-generation sequencing (NGS) tools, identifying, among others, previously undescribed anaerobic and uncultivable bacteria. In the present study, we monitored the fluctuations of this ecosystem in 15 CF patients during a 1-year follow-up period, describing for the first time, as far as we know, the presence of predator bacteria in the CF lung microbiome. In addition, a new computational model was developed to ascertain the hypothetical ecological repercussions of a prey-predator interaction in CF lung microbial communities. Fifteen adult CF patients, stratified according to their pulmonary function into mild (n = 5), moderate (n = 9), and severe (n = 1) disease, were recruited at the CF unit of the Ramón y Cajal University Hospital (Madrid, Spain). Each patient contributed three or four induced sputum samples during a 1-year follow-up period. Lung microbiota composition was determined by both cultivation and NGS techniques and was compared with the patients' clinical variables. Results revealed a particular microbiota composition for each patient that was maintained during the study period, although some fluctuations were detected without any clinical correlation. For the first time, Bdellovibrio and Vampirovibrio predator bacteria were shown in CF lung microbiota and reduced-genome bacterial parasites of the phylum Parcubacteria were also consistently detected. The newly designed computational model allows us to hypothesize that inoculation of predators into the pulmonary microbiome might contribute to the control of chronic colonization by CF pathogens in early colonization stages.IMPORTANCE The application of NGS to sequential samples of CF patients demonstrated the complexity of the organisms present in the lung (156 species) and the constancy of basic individual colonization patterns, although some differences between samples from the same patient were observed, probably related to sampling bias. Bdellovibrio and Vampirovibrio predator bacteria were found for the first time by NGS as part of the CF lung microbiota, although their ecological significance needs to be clarified. The newly designed computational model allows us to hypothesize that inoculation of predators into the lung microbiome can eradicate CF pathogens in early stages of the process. Our data strongly suggest that lower respiratory microbiome fluctuations are not necessarily related to the patient's clinical status.

Visualizing Bdellovibrio bacteriovorus by Using the tdTomato Fluorescent Protein.

Bdellovibrio bacteriovorus is a Gram-negative bacterium that belongs to the delta subgroup of proteobacteria and is characterized by a predatory life cycle. In recent years, work has highlighted the potential use of this predator to control bacteria and biofilms. Traditionally, the reduction in prey cells was used to monitor predation dynamics. In this study, we introduced pMQ414, a plasmid that expresses the tdTomato fluorescent reporter protein, into a host-independent strain and a host-dependent strain of B. bacteriovorus 109J. The new construct was used to conveniently monitor predator proliferation in real time, in different growth conditions, in the presence of lytic enzymes, and on several prey bacteria, replicating previous studies that used plaque analysis to quantify B. bacteriovorus. The new fluorescent plasmid also enabled us to visualize the predator in liquid cultures, in the context of a biofilm, and in association with human epithelial cells.

Analysis of the genome and proteome composition of Bdellovibrio bacteriovorus: indication for recent prey-derived horizontal gene transfer.

The genome/proteome composition of Bdellovibrio bacteriovorus, the predatory microorganism that preys on other Gram-negative bacteria, has been analyzed. The study elucidates that translational selection plays a major role in genome compositional variation with higher intensity compared to other deltaproteobacteria. Other sources of variations having relatively minor contributions are local GC-bias, horizontal gene transfer and strand-specific mutational bias. The study identifies a group of AT-rich genes with distinct codon composition that is presumably acquired by Bdellovibrio recently from Gram-negative prey-bacteria other than deltaproteobacteria. The proteome composition of this species is influenced by various physico-chemical factors, viz, alcoholicity, residue-charge, aromaticity and hydropathy. Cell-wall-surface-anchor-family (CSAPs) and transporter proteins with distinct amino acid composition and specific secondary-structure also contribute notably to proteome compositional variation. CSAPs, which are low molecular-weight, outer-membrane proteins with highly disordered secondary-structure, have preference toward polar-uncharged residues and cysteine that presumably help in prey-predator interaction by providing particular bonds of attachment.

A predator unmasked: life cycle of Bdellovibrio bacteriovorus from a genomic perspective.

Predatory bacteria remain molecularly enigmatic, despite their presence in many microbial communities. Here we report the complete genome of Bdellovibrio bacteriovorus HD100, a predatory Gram-negative bacterium that invades and consumes other Gram-negative bacteria. Its surprisingly large genome shows no evidence of recent gene transfer from its prey. A plethora of paralogous gene families coding for enzymes, such as hydrolases and transporters, are used throughout the life cycle of B. bacteriovorus for prey entry, prey killing, and the uptake of complex molecules.