Glycine betaine uptake by the ProXVWZ ABC transporter contributes to the ability of Mycobacterium tuberculosis to initiate growth in human macrophages

Mycobacterium tuberculosismaintains a large genetic capacity necessary for growth in different environments during infection and survival upon aerosol transmission to new hosts. Screening for bacterial RNAs produced in response to host interactions produced candidate lists where we notedproXVWZ, annotated as encoding a putative glycine betaine or proline transporter. As high surface-to-volume ratios make bacterial cells particularly vulnerable to changes in water availability, we investigated the contributions of this transporter to the ability ofM. tuberculosisto colonize macrophages. An H37RvproXVWZmutant was impaired for initial survival and intracellular growth and exhibited reduced growth at elevated medium osmolarity. This defect could be complemented by restoringproXVWZand was attributable to a failure to accumulate the compatible solute glycine betaine. We then demonstrated that ProXVWZ allowsM. tuberculosisto obtain betaine from host macrophages and thereby contributes to early steps in colonizing this niche.