Investigating the Responses of Human Epithelial Cells to Predatory Bacteria

Abstract

One beguiling alternative to antibiotics for treating multi-drug resistant infections are Bdellovibrio-and-like-organisms (BALOs), predatory bacteria known to attack human pathogens. Consequently, in this study, the responses from four cell lines (three human and one mouse) were characterized during an exposure to different predatory bacteria, Bdellovibrio bacteriovorus HD100, Bacteriovorus BY1 and Bacteriovorax stolpii EB1. TNF-α levels were induced in Raw 264.7 mouse macrophage cultures with each predator, but paled in comparison to those obtained with E. coli. This was true even though the latter strain was added at an 11.1-fold lower concentration (p < 0.01). Likewise, E. coli led to a significant (54%) loss in the Raw 264.7 murine macrophage viability while the predatory strains had no impact. Tests with various epithelial cells, including NuLi-1 airway, Caco2, HT29 and T84 colorectal cells, gave similar results, with E. coli inducing IL-8 production. The viabilities of the NuLi-1 and Caco-2 cells were slightly reduced (8%) when exposed to the predators, while T84 viability remained steady. In no cases did the predatory bacteria induce actin rearrangement. These results clearly demonstrate the gentle natures of predatory bacteria and their impacts on human cells.

Involvement of CYP1B1 in interferon γ‐induced alterations of epithelial barrier integrity

“…These cells have long been used for the in vitro study of drug absorption across the intestinal barrier (Artursson et al, 2001) and of the effects of inflammatory stimuli and pathogenic agents upon intestinal barrier function. T84 cells, for example, respond to the presence of pathogens such as the Vibrio cholerae O1 strain C6706 and Escherichia coli MG1655 by producing inflammatory cytokines (Ou et al, 2009b;Monnappa et al, 2016). The cytokine IFNγ plays a pivotal role in inflammation and it has been implicated in the disruption of the intestinal epithelial barrier (Hu and Ivashkiv, 2009;Yang et al, 2014).…”

Bacterial predation under changing viscosities

“…As BALOs are obligate predators that require a prey bacterium to complete their life cycle and their survival appears to decay fast (Hespell et al ., ), the ability to rapidly encounter prey should be a fundamental determinant of their fitness. Although their association with the human body is not firmly established, their ability to prey on pathogenic gram‐negative bacteria and the low immune responses they generate (Monnappa et al ., ; Shatzkes, Singleton, et al ., 2017) have made them a focus of interest for the development of novel antimicrobial strategies (Negus et al ., ; Shatzkes, Connell, et al ., 2017). Their application in vivo shows they can curb certain infections in mucus‐lined habitats (Shatzkes et al ., ; Willis et al ., ; De Dios Caballero et al ., ), further increasing the need to understand their behaviour under body cavity‐relevant conditions.…”

Viscosity has dichotomous effects onBdellovibrio bacteriovorusHD100 predation

“…Two of the predatory strains used in this study were isolated from a local river using the protocols described previously (Monnappa et al, 2016). Briefly, we collected freshwater from the upstream region of the Taehwa River in Ulsan.…”

“…Bdellovibrio-and-like-organisms are highly motile, Gramnegative bacteria found in various natural habitats, including soils (Jurkevitch et al, 2000;Davidov et al, 2006), rivers (Lambina et al, 1974;Monnappa et al, 2016) and oceans (Taylor et al, 1974;Pineiro et al, 2007;Peng et al, 2008;Zheng et al, 2008). The major defining feature of these microbes is their life cycle; they live as a predator and are dependent upon other Gram-negative bacteria as a source of nutrients and energy (Jurkevitch, 2007;Dwidar et al, 2012).…”