One third of the world population carries a latent tuberculosis (TB) infection, which may reactivate leading to active disease. Although TB latency has been known for many years it remains poorly understood. In particular, substances of host origin, which may induce the resuscitation of dormant mycobacteria, have not yet been described. In vitro models of dormant (“non-culturable”) cells of Mycobacterium smegmatis (mc2155) and Mycobacterium tuberculosis H37Rv were used. We found that the resuscitation of dormant M. smegmatis and M. tuberculosis cells in liquid medium was stimulated by adding free unsaturated fatty acids (FA), including arachidonic acid, at concentrations of 1.6–10 µM. FA addition enhanced cAMP levels in reactivating M. smegmatis cells and exogenously added cAMP (3–10 mM) or dibutyryl-cAMP (0.5–1 mM) substituted for FA, causing resuscitation of M. smegmatis and M. tuberculosis dormant cells. A M. smegmatis null-mutant lacking MSMEG_4279, which encodes a FA-activated adenylyl cyclase (AC), could not be resuscitated by FA but it was resuscitated by cAMP. M. smegmatis and M. tuberculosis cells hyper-expressing AC were unable to form non-culturable cells and a specific inhibitor of AC (8-bromo-cAMP) prevented FA-dependent resuscitation. RT-PCR analysis revealed that rpfA (coding for resuscitation promoting factor A) is up-regulated in M. smegmatis in the beginning of exponential growth following the cAMP increase in lag phase caused by FA-induced cell activation. A specific Rpf inhibitor (4-benzoyl-2-nitrophenylthiocyanate) suppressed FA-induced resuscitation. We propose a novel pathway for the resuscitation of dormant mycobacteria involving the activation of adenylyl cyclase MSMEG_4279 by FAs resulted in activation of cellular metabolism followed later by increase of RpfA activity which stimulates cell multiplication in exponential phase. The study reveals a probable role for lipids of host origin in the resuscitation of dormant mycobacteria, which may function during the reactivation of latent TB.

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A new method for the biotransformation of food waste is proposed. The waste is transformed to feed stock by using a novel bioremediant based on Yarrowia lipolytica, designed to be efficient in economic and environmental disposal of food waste. The toxicological studies of the product were carried out, obtained with the help of the developed technology. Biotransformation of the homogenized food waste for three days under non-sterile conditions provides a complete detoxification of the material as shown in acute and chronic toxicity. In contrast, acute test LD50 for the non-treated waste was 1220 mg/kg for mice and 3170 mg/kg for rats. The weight growth of mice and rats fed on the fermented, native preparation and in control for 10 and 28 days was assessed (multiple administration of the preparations in increasing dosages). After 10 days the mice and rats of group 1 (the waste fermented by Y. lipolytica) demonstrated 14,1% and 15,8% growth (Р<0,01). After 28 days this group exhibited 28,3% growth in mice (Р<0,001), and 25,2% in rats (Р<0,001). Group 2 (native preparation) and group 3 (biological control) demonstrated much less growth (mice/rats): 9,1/9,5 and 9,8/10,5% after 10 days; 18,6/19,1 and 21,2/22,4% after 28 days.