Experimental design considerations for in vitro microbial endocrinology investigations

Abstract

This chapter examines and critiques the different methodological approaches, which have been adopted to investigate the interactions of catecholamine neurohormones with bacteria. Adrenergic catecholamines have been shown to promote the in vitro growth of a wide range of both gram-positive and gram-negative bacterial species using growth media, which are designed to mimic the hostile bacteriostatic environment in the host. However, in recent years, it has become apparent that neurohormones are doing more than just alleviating the iron restriction caused by the mammalian transferrin in these media. In fact, it is clear that there are specific receptors in many bacteria, which can recognise epinephrine and norepinephrine resulting in increased virulence determinant expression and alterations in bacterial transcription on a global scale. Furthermore, there is now evidence that adrenergic signalling events may also be involved in the bacterial growth responses to catecholamines that have been observed previously. This analysis of the currently used methodologies is intended to assist in a more concerted approach to in vitro microbial endocrinology experiments, which identifies further bacterial genes and molecules the roles of which can be verified in future in vivo investigations.