A Comparison of the Survival of Intraperiplasmic and Attack Phase Bdellovibrios with Reduced Oxygen

Short-Term Dynamics of Bdellovibrio and Like Organisms in Lake Geneva in Response to a Simulated Climatic Extreme Event

The short time-scale dynamics of three families of Bdellovibrio and like organisms (i.e. Bdellovibrionaceae, Peredibacteraceae, and Bacteriovoracaceae) were studied on the surface waters of Lake Geneva in summer. Using mesocosms deployed nearshore in July 2019, we simulated an extreme climatic event (an input of carbon from the watershed in response to runoff from the catchment, light reduction, and mixing in response to stormy conditions) and aimed to study the impact of both abiotic and biotic factors on their dynamics. The three families of Bdellovibrio and like organisms (BALOs) showed different dynamics during the experiment. Peredibacteraceae was the most abundant group, whereas Bacteriovoracaceae was the least abundant. Compared with the other two families, the abundance of Bdellovibrionaceae did not fluctuate, remaining relatively stable over time. Environmental variables only partially explained the dynamics of these families; in particular, temperature, pH, and chloride concentrations were positively correlated with Bacteriovoracaceae, Bdellovibrionaceae, and Peredibacteraceae abundance, respectively. Prokaryote-like particles (PLPs), such as those with high DNA content (HDNA), were strongly and positively correlated with Peredibacteraceae and Bacteriovoracaceae. In contrast, no relationships were found between Bdellovibrionaceae and PLP abundance, nor between the virus-like particles (VLPs) and the different BALOs. Overall, the experiment revealed that predation was stable in the face of the simulated climatic events. In addition, we observed that Peredibacteraceae and Bacteriovoracaceae share common traits, while Bdellovibrionaceae seems to constitute a distinct category.

A Comparative Study of the Dynamics and Diversity of Bdellovibrio and Like Organisms in Lakes Annecy and Geneva

Bdellovibrio and like organisms (BALOs) are obligate bacterial predators of other Gram-negative bacteria. Here, we used quantitative PCR (qPCR) and recently developed specific primers which target the 16S rRNA gene to explore the abundance and distribution of three families of BALO belonging to the Oligoflexia class (i.e., Bdellovibrionaceae, Peredibacteraceae and Bacteriovoracaceae) over one year in the epilimnion and hypolimnion of Lakes Annecy and Geneva. Peredibacteraceae was the dominant group at all sampling points except at the bottom of Lake Geneva, where Bdellovibrionaceae was found in higher number. In addition, the abundance of BALOs increased significantly during the warmer months. Using high-throughput sequencing (Illumina Miseq), hundreds of OTUs were identified for Bdellovibrionaceae and Peredibacteraceae. Phylogenetic analysis suggests that Bdellovibrionaceae are more diverse than Peredibacteraceae and that some OTUs belong to new species of Bdellovibrionaceae. We also found that dominant OTUs were present simultaneously in the two lakes, while some others were specific to each lake, suggesting an adaptive pattern. Finally, both abundance and diversity of BALOs were poorly associated with abiotic factors except temperature, suggesting the importance of studying biotic relationships, assumed to play a greater role than physico-chemical variables in BALOs' dynamics and distribution.

Bdellovibrio and like organisms: current understanding and knowledge gaps of the smallest cellular hunters of the microbial world

Almost sixty years ago, Bdellovibrio and like organisms (BALOs) were discovered as the first obligate bacterial predators of other bacteria known to science. Since then, they were shown to be diverse and ubiquitous in the environment, and to bear astonishing ecological, physiological, and metabolic capabilities. The last decade has seen important strides made in understanding the mechanistic basis of their life cycle, the dynamics of their interactions with prey, along with significant developments towards their use in medicine, agriculture, and industry. This review details these achievements, identify current understanding and knowledge gaps to encourage and guide future BALO research.

Bdellovibrio bacteriovorus: a potential 'living antibiotic' to control bacterial pathogens

Bdellovibrio bacteriovorus is a small Deltaproteobacterium which, since its discovery, has distinguished itself for the unique ability to prey on other Gram-negative bacteria. The studies on this particular "predatory bacterium", have gained momentum in response to the rising problem of antibiotic resistance, because it could be applied as a potential probiotic and antibiotic agent. Hereby, we present recent advances in the study of B. bacteriovorus, comprehending fundamental aspects of its biology, obligatory intracellular life cycle, predation resistance, and potential applications. Furthermore, we discuss studies that pave the road towards the use of B. bacteriovorus as a "living antibiotic" in human therapy, focussing on its interaction with biofilms, the host immune response, predation susceptibility and in vivo application models. The available data imply that it will be possible to upgrade this predator bacterium from a predominantly academic interest to an instrument that could confront antibiotic resistant infections.

Drug Resistance and the Prevention Strategies in Food Borne Bacteria: An Update Review

Antibiotic therapy is among the most important treatments against infectious diseases and has tremendously improved effects on public health. Nowadays, development in using this treatment has led us to the emergence and enhancement of drug-resistant pathogens which can result in some problems including treatment failure, increased mortality as well as treatment costs, reduced infection control efficiency, and spread of resistant pathogens from hospital to community. Therefore, many researches have tried to find new alternative approaches to control and prevent this problem. This study, has been revealed some possible and effective approaches such as using farming practice, natural antibiotics, nano-antibiotics, lactic acid bacteria, bacteriocin, cyclopeptid, bacteriophage, synthetic biology and predatory bacteria as alternatives for traditional antibiotics to prevent or reduce the emergence of drug resistant bacteria.

Ecological Therapeutic Opportunities for Oral Diseases

The three main oral diseases of humans, that is, caries, periodontal diseases, and oral candidiasis, are associated with microbiome shifts initiated by changes in the oral environment and/or decreased effectiveness of mucosal immune surveillance. In this review, we discuss the role that microbial-based therapies may have in the control of these conditions. Most investigations on the use of microorganisms for management of oral disease have been conducted with probiotic strains with some positive but very discrete clinical outcomes. Other strategies such as whole oral microbiome transplantation or modification of community function by enrichment with health-promoting indigenous oral strains may offer more promise, but research in this field is still in its infancy. Any microbial-based therapeutics for oral conditions, however, are likely to be only one component within a holistic preventive strategy that should also aim at modification of the environmental influences responsible for the initiation and perpetuation of microbiome shifts associated with oral dysbiosis.

Agriculture and food animals as a source of antimicrobial-resistant bacteria

One of the major breakthroughs in the history of medicine is undoubtedly the discovery of antibiotics. Their use in animal husbandry and veterinary medicine has resulted in healthier and more productive farm animals, ensuring the welfare and health of both animals and humans. Unfortunately, from the first use of penicillin, the resistance countdown started to tick. Nowadays, the infections caused by antibiotic-resistant bacteria are increasing, and resistance to antibiotics is probably the major public health problem. Antibiotic use in farm animals has been criticized for contributing to the emergence of resistance. The use and misuse of antibiotics in farm animal settings as growth promoters or as nonspecific means of infection prevention and treatment has boosted antibiotic consumption and resistance among bacteria in the animal habitat. This reservoir of resistance can be transmitted directly or indirectly to humans through food consumption and direct or indirect contact. Resistant bacteria can cause serious health effects directly or via the transmission of the antibiotic resistance traits to pathogens, causing illnesses that are difficult to treat and that therefore have higher morbidity and mortality rates. In addition, the selection and proliferation of antibiotic-resistant strains can be disseminated to the environment via animal waste, enhancing the resistance reservoir that exists in the environmental microbiome. In this review, an effort is made to highlight the various factors that contribute to the emergence of antibiotic resistance in farm animals and to provide some insights into possible solutions to this major health issue.

Bdellovibrio bacteriovorus : A future antimicrobial agent?

Bdellovibrio and like organisms (BALOs) are small, predatory, Deltaproteobacteria that prey on other Gram-negative pathogens. Many authors have unfolded the possible use of BALOs as biological control agents in environmental as well as medical microbiological settings. They are found strongly associated with natural biofilms and recent studies have shown that effective predation occurs in these naturally occurring bacterial communities. Periodontal infections could also be an interesting target for the application of BALOs as biological Gram-negative bacteria and therefore potentially susceptible to BALOs antimicrobial agents. This proposition is based on the fact that almost all periodontal pathogens are predation. Accordingly, this review aims to present the evolution toward applying Bdellovibrio bacteriovorus as an antibacterial agent to deal with oral infections, general medical conditions, environmental and industrial issues.

Measurement of predation and biofilm formation under different ambient oxygen conditions using a simple gasbag-based system

Bdellovibrio bacteriovorus and Micavibrio aeruginosavorus are Gram-negative bacteria characterized by predatory behavior. The aim of this study was to evaluate the ability of the predators to prey in different oxygen environments. When placed on an orbital shaker, a positive association between the rate of aeration and predation was observed. To further examine the effects of elevated ambient oxygen levels on predation, a simple gasbag system was developed. Using the system, we were able to conduct experiments at ambient oxygen levels of 3% to 86%. When placed in gasbags and inflated with air, 50% O2, and 100% O2, positive predation was seen on both planktonic and biofilm-grown prey cells. However, in low-oxygen environments, predatory bacteria were able to attack only prey cells grown as biofilms. To further evaluate the gasbag system, biofilm development of Gram-positive and Gram-negative microorganisms was also measured. Although the gasbag system was found to be suitable for culturing bacteria that require a low-oxygen environment, it was not capable of supporting, with its current configuration, the growth of obligate anaerobes in liquid or agar medium.

Effects of orally administered Bdellovibrio bacteriovorus on the well-being and Salmonella colonization of young chicks

Bdellovibrio bacteriovorus is a bacterium which preys upon and kills Gram-negative bacteria, including the zoonotic pathogens Escherichia coli and Salmonella. Bdellovibrio has potential as a biocontrol agent, but no reports of it being tested in living animals have been published, and no data on whether Bdellovibrio might spread between animals are available. In this study, we tried to fill this knowledge gap, using B. bacteriovorus HD100 doses in poultry with a normal gut microbiota or predosed with a colonizing Salmonella strain. In both cases, Bdellovibrio was dosed orally along with antacids. After dosing non-Salmonella-infected birds with Bdellovibrio, we measured the health and well-being of the birds and any changes in their gut pathology and culturable microbiota, finding that although a Bdellovibrio dose at 2 days of age altered the overall diversity of the natural gut microbiota in 28-day-old birds, there were no adverse effects on their growth and well-being. Drinking water and fecal matter from the pens in which the birds were housed as groups showed no contamination by Bdellovibrio after dosing. Predatory Bdellovibrio orally administered to birds that had been predosed with a gut-colonizing Salmonella enterica serovar Enteritidis phage type 4 strain (an important zoonotic pathogen) significantly reduced Salmonella numbers in bird gut cecal contents and reduced abnormal cecal morphology, indicating reduced cecal inflammation, compared to the ceca of the untreated controls or a nonpredatory ΔpilA strain, suggesting that these effects were due to predatory action. This work is a first step to applying Bdellovibrio therapeutically for other animal, and possibly human, infections.

Predation of human pathogens by the predatory bacteria Micavibrio aeruginosavorus and Bdellovibrio bacteriovorus

AIMS

The focus of this study was to evaluate the potential use of the predatory bacteria Bdellovibrio bacteriovorus and Micavibrio aeruginosavorus to control the pathogens associated with human infection.

METHODS AND RESULTS

By coculturing B. bacteriovorus 109J and M. aeruginosavorus ARL-13 with selected pathogens, we have demonstrated that predatory bacteria are able to attack bacteria from the genus Acinetobacter, Aeromonas, Bordetella, Burkholderia, Citrobacter, Enterobacter, Escherichia, Klebsiella, Listonella, Morganella, Proteus, Pseudomonas, Salmonella, Serratia, Shigella, Vibrio and Yersinia. Predation was measured in single and multispecies microbial cultures as well as on monolayer and multilayer preformed biofilms. Additional experiments aimed at assessing the optimal predation characteristics of M. aeruginosavorus demonstrated that the predator is able to prey at temperatures of 25-37°C but is unable to prey under oxygen-limiting conditions. In addition, an increase in M. aeruginosavorus ARL-13 prey range was also observed.

CONCLUSIONS

Bdellovibrio bacteriovorus and M. aeruginosavorus have an ability to prey and reduce many of the multidrug-resistant pathogens associated with human infection.

SIGNIFICANCE AND IMPACT OF THE STUDY

Infectious complications caused by micro-organisms that have become resistant to drug therapy are an increasing problem in medicine, with more infections becoming difficult to treat using traditional antimicrobial agents. The work presented here highlights the potential use of predatory bacteria as a biological-based agent for eradicating multidrug-resistant bacteria, with the hope of paving the way for future studies in animal models.

Predation of oral pathogens by Bdellovibrio bacteriovorus 109J

Periodontal diseases are multifactorial infections elicited by a complex of primarily gram-negative bacteria that interact with host tissues and lead to the destruction of the periodontal structures. Bdellovibrio bacteriovorus is a gram-negative bacterium that preys upon other gram-negative bacteria. It was previously shown that B. bacteriovorus has an ability to attack and remove surface-attached bacteria or biofilms. In this study, we examined the host specificity of B. bacteriovorus strain 109J and its ability to prey on oral pathogens associated with periodontitis, including; Aggregatibacter actinomycetemcomitans, Eikenella corrodens, Fusobacterium nucleatum, Prevotella intermedia, Porphyromonas gingivalis and Tannerella forsythia. We further demonstrated that B. bacteriovorus 109J has an ability to remove biofilms of Ei. corrodens as well as biofilms composed of A. actinomycetemcomitans. Bdellovibrio bacteriovorus was able to remove A. actinomycetemcomitans biofilms developed on hydroxyapatite surfaces and in the presence of saliva, as well as to detach metabolically inactive biofilms. Experiments aimed at enhancing the biofilm removal aptitude of B. bacteriovorus with the aid of extracellular-polymeric-substance-degrading enzymes demonstrated that proteinase-K inhibits predation. However, treating A. actinomycetemcomitans biofilms with DspB, a poly-N-acetylglucosamine (PGA) -hydrolysing enzyme, increased biofilm removal. Increased biofilm removal was also recorded when A. actinomycetemcomitans PGA-defective mutants were used as host cells, suggesting that PGA degradation could enhance the removal of A. actinomycetemcomitans biofilm by B. bacteriovorus.

Bdellovibrio bacteriovorus attacks Aggregatibacter actinomycetemcomitans

Periodontitis is a polymicrobial infectious disease primarily associated with Gram-negative periodontopathogens. Bdellovibrio and like organisms are predatory bacteria that feed on Gram-negative bacteria. This study investigated whether predatory bacteria can attack Aggregatibacter actinomycetemcomitans. Therefore, A. actinomycetemcomitans was challenged with the predator Bdellovibrio bacteriovorus under conditions simulating the oral cavity. The reduction of planktonic A. actinomycetemcomitans was quantified via bacterial culture, and the development of predatory bacteria was monitored with quantitative real-time PCR. The destruction of A. actinomycetemcomitans biofilms by B. bacteriovorus was quantified by crystal violet staining and visualized by scanning electron microscopy. The in vitro results show that B. bacteriovorus can attack, prey on, and kill A. actinomycetemcomitans and suggest a potential for B. bacteriovorus as a living antibiotic for the prevention and treatment of periodontitis.

Predation in the presence of decoys: an inhibitory factor on pathogen control by bacteriophages or bdellovibrios in dense and diverse ecosystems

Several attempts have been made at the removal of specific pathogens from the intestinal microflora using either bacteriophages or "predatory" bacteria such as Bdellovibrio spp. To date these attempts have had mixed success. A mechanism explaining these findings based on competitive hindrance by non-prey, or decoy species is put forward. It is shown that this hindrance tends to damp out predator-prey oscillations, and therefore reduces the probability of prey extinction. Possible experiments to verify this theory are discussed. The decoy effect may play a role in any system with high densities of bacteria or other particulate matter, such as activated sludge or biofilms.