Stress Responses, Adaptation, and Virulence of Bacterial Pathogens During Host Gastrointestinal Colonization

Abstract

Invading pathogens are exposed to a multitude of harmful conditions imposed by the host gastrointestinal tract and immune system. Bacterial defenses against these physical and chemical stresses are pivotal for successful host colonization and pathogenesis. Enteric pathogens, which are encountered due to the ingestion of or contact with contaminated foods or materials, are highly successful at surviving harsh conditions to colonize and cause the onset of host illness and disease. Pathogens such as Campylobacter, Helicobacter, Salmonella, Listeria, and virulent strains of Escherichia have evolved elaborate defense mechanisms to adapt to the diverse range of stresses present along the gastrointestinal tract. Furthermore, these pathogens contain a multitude of defenses to help survive and escape from immune cells such as neutrophils and macrophages. This chapter focuses on characterized bacterial defenses against pH, osmotic, oxidative, and nitrosative stresses with emphasis on both the direct and indirect mechanisms that contribute to the survival of each respective stress response.

Characterisation of Aerotolerant Forms of a Robust Chicken Colonizing Campylobacter coli

“…The ability to withstand atmospheric oxygen is also relevant to survival on chicken meat and is therefore of public health significance. Aerotolerance is related, at least in part, to oxidative stress resistance which has been shown to be a colonization factor for chickens and a virulence factor for human infection (Hermans et al, 2011; Bolton, 2015; Flint et al, 2016a). …”

“…Common sources of oxidative free radicals include the organisms’ own respiratory metabolism, the ambient atmosphere in the extra-intestinal environment, and reactive oxygen species (ROS) generated by phagocytic or cytotoxic cells involved in the host immune response (Atack and Kelly, 2009). ROS damage DNA, proteins and lipids, limiting growth or killing the bacteria (Flint et al, 2016a). C. jejuni lacks several of the key oxidative stress response regulators identified in Escherichia coli , such as SoxRS, OxyR or Crp, and whereas E. coli possesses three separate superoxide dismutase and two catalase enzymes, C. jejuni encodes only one of each (Parkhill et al, 2000; Imlay, 2013; Flint et al, 2016b).…”

The Campylobacter jejuni Type VI Secretion System Enhances the Oxidative Stress Response and Host Colonization

“…During host colonization and infection, C. jejuni is exposed to conditions in the host gastrointestinal tract that present as physical and chemical stresses, including oxidative stress (Kim et al, 2015;Flint et al, 2016). Oxidative stress involves the generation of reactive oxygen species (ROS) that cause damage to nucleic acids, membranes and proteins of bacteria.…”

An Osmoregulatory Mechanism Operating through OmpR and LrhA Controls the Motile-Sessile Switch in the Plant Growth-Promoting Bacterium Pantoea alhagi

“…Osmotic stress adaptation is critical for bacterial survival in dynamic environments, and in particular, for symbionts or pathogens to colonize and survive in host niches (52,53). The paradigm of the two-component systems involved in bacterial response to osmotic stress is the EnvZ-OmpR system, of which EnvZ acts as a sensor responding to increasing extracellular osmolality and phosphorylates OmpR (47,54).…”