Abstract
Mycobacteria are classified into two groups, fast- and slow-growing. Often, fast-growing mycobacteria are assumed to have a higher metabolic activity than their slower counterparts, but in mature biofilms this assumption might not be correct. Indeed, when measuring the metabolic activity of mycobacterial biofilms with two independent non-invasive techniques (isothermal microcalorimetry and tunable diode laser absorption spectrometry), mature biofilms of slow- and fast-growing species appeared more alike than expected. Metabolic heat production rate was 2298 ± 181 µW for M. smegmatis and 792 ± 81 µW for M. phlei, while M. tuberculosis and M. bovis metabolic heat production rates were between these values. These small differences were further confirmed by similar oxygen consumption rates (3.3 ± 0.2 nMole/s and 1.7 ± 0.3 nMole/s for M. smegmatis and M. tuberculosis, respectively). These data suggest that the metabolic potential of slow-growing mycobacterial biofilms has been underestimated, particularly for pathogenic species.
Highlights
Since its discovery in 1882, there has been significant improvement in our understanding of Mycobacterium tuberculosis
Microbiologists often assume that fast-growing mycobacteria such as M. phlei or M. smegmatis have a higher metabolic activity compared to their slow-growing counterparts such as M. tuberculosis and M. bovis
Mature biofilms of M. smegmatis produced on nylon filters showed different behavior than planktonic cultures or freshly inoculated biofilm (Supplementary Figures S1 and S2)
Summary
Since its discovery in 1882, there has been significant improvement in our understanding of Mycobacterium tuberculosis. Drug resistance is linked to several genetic determinants, while drug persistence is the survival of a microbial subpopulation from the lethal effect of a drug This subpopulation might later resume growth and lead to a persistent infection. Drug resistance and persistence are linked to biofilm formation. M. tuberculosis biofilms (or biofilm-like structures) are observed in primary lesion residual necrosis and in coating cavities[15, 16] Such biofilm formation by M. tuberculosis and other mycobacteria has been shown to reduce their sensitivity to antimycobacterial agents[17, 18]. In mature biofilms exist to support this belief with direct evidence Such knowledge about the metabolic activity of mature biofilms has critical implications for understanding M. tuberculosis biofilm physiology (including extra-pulmonary cases), drug development, and patient care. Heat production rate is directly linked to the overall metabolism (substrate consumption and byproduct release27) as shown by the glycerol respiration equation (Equation 1)
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call