Trehalose Is Required for Growth of Mycobacterium smegmatis

Abstract

Mycobacteria contain high levels of the disaccharide trehalose in free form as well as within various immunologically relevant glycolipids such as cord factor and sulfolipid-1. By contrast, most bacteria use trehalose solely as a general osmoprotectant or thermoprotectant. Mycobacterium tuberculosis and Mycobacterium smegmatis possess three pathways for the synthesis of trehalose. Most bacteria possess only one trehalose biosynthesis pathway and do not elaborate the disaccharide into more complex metabolites, suggesting a distinct role for trehalose in mycobacteria. We disabled key enzymes required for each of the three pathways in M. smegmatis by allelic replacement. The resulting trehalose biosynthesis mutant was unable to proliferate and enter stationary phase unless supplemented with trehalose. At elevated temperatures, however, the mutant was unable to proliferate even in the presence of trehalose. Genetic complementation experiments showed that each of the three pathways was able to recover the mutant in the absence of trehalose, even at elevated temperatures. From a panel of trehalose analogs, only those with the native ␣,␣-(1,1) anomeric stereochemistry rescued the mutant, whereas alternate stereoisomers and general osmo-and thermoprotectants were inactive. These findings suggest a dual role for trehalose as both a thermoprotectant and a precursor of critical cell wall metabolites.Trehalose (␣-D-glucopyranosyl-(1,1)-␣-D-glucopyranoside, Fig.

Mycobacterial outer membrane is a lipid bilayer and the inner membrane is unusually rich in diacyl phosphatidylinositol dimannosides

“…In contrast, M. smegmatis OM contained bound MAs (Table 1) in the inner leaflet, as expected from the Minnikin model (1), instead of CLs. This obligatory presence of MAs in the OM is consistent with the observation that mycobacteria cannot (but C. glutamicum can) survive without trehalose, which is needed for the export of MA residues to the OM (13,14).…”

“…S4). TMM has been believed to be involved in transporting MAs from their site of synthesis in the cytosol to the outer cell envelope, where they may be esterified to the cell wall or remain as trehalose dimyoclate (TDM) (12,13). In contrast to these studies, other workers (14) indicated that in C. glutamicum TMM is synthesized in the outer cell wall and hence cannot be present in the IM.…”

Organic solutes in Rubrobacter xylanophilus: the first example of di-myo-inositol-phosphate in a thermophile

“…Generally, glutamate, proline and ectoine are the most abundant compatible solutes of those Bacteria, while a few high G + C Gram-Positive Bacteria (Phylum Actinobacteria) studied, namely corynebacteria and streptomycetes accumulate trehalose, proline, glutamine and alanine under osmotic stress (Shimakata and Minatogawa 2000;Wolf et al 2003). These organisms as well as mycobacteria accumulate a low steady-state trehalose pool, and in some Streptomyces sp., trehalose is also involved in spore germination being implicated in their heat and desiccation resistance (McBride and Ensign 1987;Woodruff et al 2004 Glycine betaine (GB), a common compatible solute of mesophilic prokaryotes, was a minor solute in R. xylanophilus grown in Thermus medium, indicating that it was taken up, along with glutamate, from the yeast extract and tryptone. This solute cannot, however, have a role in osmotic adjustment in this organism because of the minor amounts accumulated.…”

A Unique Combination of Genetic Systems for the Synthesis of Trehalose in Rubrobacter xylanophilus : Properties of a Rare Actinobacterial TreT

“…While some of these organisms can have two or even three pathways for trehalose synthesis, most bacteria as well as plants and animals have only the Tps/Tpp pathway (2,38,39). The TreS pathway is found almost exclusively in bacteria, and the TreT pathway is present mainly in hyperthermophilic bacteria and archaea (7,17,29,33).…”