Microbes in the animal's gut: getting them onside

摘要

Microbes in the digestive tract play a pivotal role in determining the physiological, metabolic and health status of the host. In most instances the microbial communities within the digestive tract benefit the host through the provision of nutrients(e.g., B vitamins, volatile fatty acids, protein), degradation of toxins or preclusion of potential pathogens. Previously, microbes were viewed as opportunistic passengers which thrived within the environmentally controlled conditions of the mammalian digestive tract. More recent evidence suggests that microbial communities within the digestive tract are highly structured and in a state of continuous adaptation. Adaptation of whole microbial communities is achieved through a complex form of chemical communication known as quorum-sensing. Some of the members of these communities communicate with host intestinal cells and cause dramatic changes in intestinal architecture subsequent to colonization. In many instances the establishment of microbial pathogens or the transition of a previously nonpathogenic bacteria to a pathogenic form is likely a result of a communication breakdown among commensal bacterial populations or with host cells. Manipulation of the microbial populations of the digestive tract has been a long term goal of clinicians, microbiologists and nutritionists. In North America, antibiotics are the primary means of promoting desired changes in the composition of gastrointestinal microbial populations. However, the use of antibiotics in animal production is under increasing scrutiny as data emerges that suggests a linkage between antibiotic use in livestock and increased prevalence of antibiotic resistant bacteria. This has prompted a renewed interest in the efficacy of potential alternatives to antibiotics such as phage therapy, antibody therapy, probiotics, prebiotics and vaccines. Undoubtedly, the success or failure of these approaches will depend in part on their potential to alter the factors that enable microorganisms to persist and reproduce in the digestive tract.