Dormant forms of Mycobacterium smegmatis with distinct morphology

Abstract

Cultivation of Mycobacterium smegmatis cells in a nitrogen-limited minimal medium (SR-1) followed by prolonged storage at room temperature without shaking resulted in the gradual accumulation of morphologically distinct ovoid forms characterized by (i) low metabolic activity; (ii) elevated resistance to antibiotics and to heat treatment; and (iii) inability to produce colonies on standard agar plates (non-platable cells). Detailed microscopic examination confirmed that ovoid cells possessed an intact cell envelope, specific fine structure and large electron-transparent bodies in the cytoplasm. Cell staining with Nile red and analysis of the lipid content by TLC revealed the presence of significant amounts of apolar lipids in these bodies. The ovoid forms could be stored for significant periods (up to 5 months) and resuscitated afterwards in a modified Sauton's medium. Importantly, resuscitation of ovoid cells was accompanied by their transformation into the typical rod-shaped cells. We suggest that the observed ovoid cells represent dormant forms, resembling morphologically distinct cells of Mycobacterium tuberculosis previously isolated from tuberculosis patients and infected animals.

Simultaneous staining of sputum smears for acid-fast and lipid-containing Myobacterium tuberculosis can enhance the clinical evaluation of antituberculosis treatments

“…Cream cells had a size and appearance between the green and red cells [31,32]; examples are shown in Figure 6. We counted cells on consecutive images until all were counted or the total number of cells counted was 100 or more.…”

Morphological Alteration and Survival of Burkholderia pseudomallei in Soil Microcosms

“…Moreover, several studies have reported that VBNC cells had higher physical and chemical resistance than culturable cells. [44][45][46] Our investigation into the fate of B. pseudomallei during a 120-day period in various soil microcosms using the LIVE/ DEAD ® BacLight ™ assay demonstrated both the culturability and viability of a B. pseudomallei environmental isolate grown in a control soil microcosm ( Figure 4A and B). Our results strengthen previous results demonstrating that endemic soils provided environmental niches for the survival of B. pseudomallei.…”

Electrochemical monitoring of the metabolic activity of mycobacteria in culture

“…Some of these methods include the following: measurement of the novo protein synthesis, reduction of tetrazolium salts as an indication of respiratory activity (McDougald et al 1998), evaluation of carbohydrate consumption (Gillespie et al 1986), analysis of cellular structure by microscopy (Anuchin et al 2009;Berney and Cook 2010) and detection of genomic and transcriptomic differences (Pai et al 2000). These methods are manual, costly, timeconsuming techniques that, in some cases, are not sensitive enough for analyzing a small population of bacteria.…”