Article Figures & Data
Figures
- FIG. 1.
Morphology of B. cereus growing in LB broth (A to E) or SESOM+ (F to J) at 30°C with shaking at 150 rpm for 4 h (A and F), 6 h (B and G), 10 h (C and H), 24 h (D and I), and 48 h (E and J). Culture samples were stained with Live/Dead BacLight stain and visualized by epifluorescence microscopy.
- FIG. 2.
Morphology of soil Bacillus isolates 9 (A), 20 (B), 12 (C), and 17 (D) and B. subtilis subsp. subtilis Marburg (E) cultured in SESOM+ for 24 h at 30°C with shaking at 150 rpm. Culture samples were stained with Live/Dead BacLight stain and visualized by epifluorescence microscopy.
- FIG. 3.
Culturable counts (A) and percentage of spores (B) of B. cereus in SESOM+-saturated artificial soil microcosms located in wells in SESOM+ or LB agar and incubated for 96 h at 30°C. Data are averages of three separate experiments, and error bars indicate standard errors of the means.
- FIG. 4.
Translocation of B. cereus and other soil Bacillus species through artificial soil microcosms by elongation and division of cells in chains. B. cereus point inoculated at the center of a soil microcosm (A) was able to translocate through the soil matrix containing a 1 mM concentration of the motility inhibitor l-ethionine, as demonstrated by outgrowths onto the surrounding agar surface (B). The bundles of chains observed in ASM at 72 h of incubation (C) were reminiscent of the multicellularity as induced in liquid SESOM after 10 h of incubation with shaking at 30°C (D). Samples were stained with Live/Dead BacLight stain and viewed by CLSM.
- FIG. 5.
Swimming (A and B) and swarming (C and D) motility of B. cereus ATCC 14579 in SESOM swim and swarm agar without (A and C) and with (B and D) a 1 mM concentration of the motility inhibitor l-ethionine, viewed after incubation at 30°C for 72 h.
Tables
- TABLE 1.
Characteristics of growth parameters, yields, and sporulation of B. cereus under different culture conditionsa
Culture condition (inoculum and medium) OD at 24 hb Duration of lag phase (min) Generation time (min)c CFU/ml after 8 h (n = 12) CFU/ml after 24 h (n = 12) Total % Spores Total % Spores VI into SESOM 0.145 0 48.3 ± 1.3 ND ND 2.3 ± 0.1 × 106 144.4 ± 11.1d SI into SESOM 0.155 ND ND ND ND 3.5 ± 0.6 × 106 133.2 ± 14.3d VI into LB 2.105 80 26.2 ± 0.6 4.4 ± 0.2 × 108 0.0 ± 0.0 5.0 ± 0.2 × 108 0.0 ± 0.0 VI into SESOM+ 0.265 0 36.9 ± 0.8 2.1 ± 0.1 × 107 0.0 ± 0.0 2.8 ± 0.3 × 107 96.5 ± 2.4 SI into LB 2.311 160 26.1 ± 1.4 3.9 ± 0.3 × 108 0.0 ± 0.0 5.6 ± 1.0 × 108 0.0 ± 0.0 SI into SESOM+ 0.269 200 38.1 ± 1.8 1.1 ± 0.1 × 107 0.0 ± 0.0 1.8 ± 0.2 × 107 96.3 ± 2.6 VI into MOPS+e 0.006 No growth No growth ND ND 3.6 ± 0.2 × 105 0.0 ± 0.0 SI into MOPS+ 0.008 No growth No growth ND ND 2.5 ± 0.2 × 105 95.8 ± 4.2 ↵a Incubation was at 30°C with shaking at 150 rpm. Data are presented as the mean ± standard error of the mean. VI, vegetative inoculum, inoculated to an initial density of 105 CFU/ml; SI, spore inoculum, inoculated to an initial density of 105 CFU/ml; ND, not determined.
↵b OD, optical density (λ = 546 nm).
↵c n = 6.
↵d The culturable count may constitute an underestimation due to clumping, while spores may be released from clumps during pasteurization, leading to a higher spore count than the culturable count.
↵e MOPS+, 10 mM MOPS buffer plus additives (see Materials and Methods for details).
