Bdellovibrio bacteriovorus is a predatory bacterium which attacks and consumes other bacterial strains, including the well known pathogens E. coli O157：H7, Salmonella typhimurium and Helicobacter pylori. This remarkable activity has been the focus of research for nearly five decades, with exciting practical applications to medical, agriculture and farming practices recently being published. This article reviews many of the exciting steps research into this bacterium, and similar bacteria, has taken, focusing primarily on their use as both an antibiotic to remove harmful and pathogenic bacteria and as a probiotic to help curb and control the bacterial populations within the intestinal tract. Owing to the unique and dual nature of this bacterium, this review proposes the use of "amphibiotic" to describe these bacteria and their activities. [BMB reports 2012; 45(2): 71-78]

In this paper, the different applications of butyric acid and its current and future production status are highlighted, with a particular emphasis on the biofuels industry. As such, this paper discusses different issues regarding butyric acid fermentations and provides suggestions for future improvements and their approaches.

Bdellovibrio bacteriovorus HD100 is a predatory bacterium that attacks many Gram-negative human pathogens. A serious drawback of this strain, however, is its ineffectiveness against Gram-positive strains, such as the human pathogen Staphylococcus aureus. Here we demonstrate that the extracellular proteases produced by a host-independent B. bacteriovorus (HIB) effectively degrade/inhibit the formation of S. aureus biofilms and reduce its virulence. A 10% addition of HIB supernatant caused a 75% or greater reduction in S. aureus biofilm formation as well as 75% dispersal of pre-formed biofilms. LC-MS-MS analyses identified various B. bacteriovorus proteases within the supernatant, including the serine proteases Bd2269 and Bd2321. Tests with AEBSF confirmed that serine proteases were active in the supernatant and that they impacted S. aureus biofilm formation. The supernatant also possessed a slight DNAse activity. Furthermore, treatment of planktonic S. aureus with the supernatant diminished its ability to invade MCF-10a epithelial cells by 5-fold but did not affect the MCF-10a viability. In conclusion, this study illustrates the hitherto unknown ability of B. bacteriovorus to disperse Gram-positive pathogenic biofilms and mitigate their virulence.

Artificial cells that encapsulate DNA-programmable protein expression machinery are emerging as an attractive platform for studying fundamental cellular properties and applications in synthetic biology. However, interfacing these artificial cells with the complex and dynamic chemical environment remains a major and urgent challenge. We demonstrate that the repertoire of molecules that artificial cells respond to can be expanded by synthetic RNA-based gene switches, or riboswitches. We isolated an RNA aptamer that binds histamine with high affinity and specificity and used it to design robust riboswitches that activate protein expression in the presence of histamine. Finally, the riboswitches were incorporated in artificial cells to achieve controlled release of an encapsulated small molecule and to implement a self-destructive kill-switch. Synthetic riboswitches should serve as modular and versatile interfaces to link artificial cell phenotypes with the complex chemical environment.

Bdellovibrio bacteriovorus is a predatory bacterium that attacks a wide range of Gram-negative bacterial pathogens and is proposed to be a potential living antibiotic. In this study, we evaluated the effects of indole, a bacterial signalling molecule commonly produced within the gut, on the predatory ability of B. bacteriovorus HD100. Indole significantly delayed predation on Escherichia coli MG1655 and Salmonella enterica KACC 11595 at physiological concentrations (0.25 to 1 mM) and completely inhibited predation when present at 2 mM. Microscopic analysis revealed that indole blocked the predator from attacking the prey. Furthermore, indole was not toxic to the predator but slowed down its motility. Microarray and reverse transcription quantitative polymerase chain reaction (RT-qPCR) analyses confirmed that as the gene group showing the greatest downregulation in the presence of indole was flagellar assembly genes. Indole also caused a wide spectrum changes in gene expression including general downregulation of genes involved in ribosome assembly. Furthermore, indole addition to the predatory culture after the entrance of B. bacteriovorus into the prey periplasm slowed down bdelloplast lysis. In conclusion, indole can have significant impacts on the predation efficiency, which should be taken into consideration especially if B. bacteriovorus is to be applied as a probiotic or living antibiotic.