Efflux of bile acids in Lactobacillus reuteri is mediated by ATP

Abstract

To study whether an active bile acid (BA) efflux occurs in Lactobacillus reuteri CRL 1098 as well as the nature (ATP or proton motive force [PMF] mediated primary transport) of the BA extrusion mechanism. BAs are powerful detergents which disorganize the lipid bilayer structure of cellular membranes. Specific bile resistance mechanisms (bile efflux, bile salt hydrolysis, and intrinsic architecture and composition of cell membrane the most prevalent) have been described in intestinal bacteria. L. reuteri, showed a significant degree of resistance to the toxic action of BA and the presence of an active efflux ATP-dependent of conjugated (taurocholic [TCA]) and free (cholic [CA]) BA in the CRL 1098 strain is now reported. However, due the high pKa (5.5) of cholic acid (CA) compared with the conjugated species, a significant fraction (between 35 and 50% at pH 6.5 and 5.2, respectively) of free BA also diffused passively, even in the absence of ATP. To our knowledge, our results represent the first evidence of ATP as the energy source involved in the BA extrusion in L. reuteri.

Intestinal transport and metabolism of bile acids

“…The mechanisms for bacterial resistance to bile acids include expression of effl ux pumps and enzymes that biotransform bile acids. The bile acid effl ux systems include ATP-dependent (e.g., members of the ABC superfamily) (168)(169)(170)(171)(172) and proton motive force-dependent carriers (e.g., members of the resistance-nodulation-division family and major facilitator superfamily) ( 173, 174 ) and appear to be a common mechanism for bile acid resistance by gut bacteria. Indeed, expression of many of these effl ux systems is bile acid-inducible and their contribution to growth and bile resistance has been demonstrated directly by functional genetics ( 169, 172, 175 ).…”

Bile resistance mechanisms in Lactobacillus and Bifidobacterium

“…Overall, bile response is a multifactorial phenomenon, implicating a variety of processes addressed toward detoxification of bile and counteracting the deleterious effect on bacterial structures, as described on the following paragraphs. Active efflux of bile acids/salts (Pfeiler and Klaenhammer, 2009; Bustos et al, 2011; Ruiz et al, 2012a,b), bile salt hydrolysis (Kumar et al, 2006; Lambert et al, 2008), and changes in the architecture/composition of cell membrane and cell wall (Gómez-Zavaglia et al, 2002; Taranto et al, 2003; Ruiz et al, 2007) appear to be the most prevalent bile-specific mechanisms mediating resistance in both genera. In addition, general stress response, protection against oxidative damages, as well as global glycolytic reorganizations are other common consequences of bile exposure, that might be employed to counteract some of the cellular damage caused by these compounds ( Figure 1 ; Table 1 ; Hamon et al, 2011; Ruiz et al, 2011; Alcantara and Zuñiga, 2012).…”

“…In Lactobacillus johnsonii , a functional taurocholic and cholic acid antiporter belonging to the major facilitator superfamily, CbsT2 , has also been described although its contribution to bile tolerance has not been demonstrated by means of functional genetics (Elkins and Savage, 2003). Furthermore, L. reuteri efflux of both free and conjugated bile acids has been demonstrated and ATP was found to be the main force driving the extrusion activity (Bustos et al, 2011). …”

Gastrointestinal stress as innate defence against microbial attack

“…As mentioned above in 2Á3.1, bile tolerance is an important property for the survival of beneficial microbes in the small intestine. Bile stress response includes a plethora of phenomenon, that include active efflux of bile salts (Bustos et al 2011;Ruiz et al 2012aRuiz et al , 2012b, hydrolysis of bile salts (Lambert et al 2008), remodelling of the cell membrane and cell wall (Ruiz et al 2007) etc. Bile acid resistance is an added advantage for the microbes to get colonized in the human GIT (Yokota and Moraes 2012;Horackova et al 2018).…”