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Water surface tension modulates the swarming mechanics of Bacillus subtilis.

Ke WJ, Hsueh YH, Cheng YC, Wu CC, Liu ST - Front Microbiol (2015)

Bottom Line: Many Bacillus subtilis strains swarm, often forming colonies with tendrils on agar medium.It is known that B. subtilis swarming requires flagella and a biosurfactant, surfactin.B. subtilis colonies were found to contain water, and when a low amount of surfactin is produced, the water surface tension of the colony restricts expansion, causing bacterial density to rise.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Immunology, Chang Gung University Taoyuan, Taiwan ; Research Center for Bacterial Pathogenesis, Chang Gung University Taoyuan, Taiwan.

ABSTRACT
Many Bacillus subtilis strains swarm, often forming colonies with tendrils on agar medium. It is known that B. subtilis swarming requires flagella and a biosurfactant, surfactin. In this study, we find that water surface tension plays a role in swarming dynamics. B. subtilis colonies were found to contain water, and when a low amount of surfactin is produced, the water surface tension of the colony restricts expansion, causing bacterial density to rise. The increased density induces a quorum sensing response that leads to heightened production of surfactin, which then weakens water surface tension to allow colony expansion. When the barrier formed by water surface tension is breached at a specific location, a stream of bacteria swarms out of the colony to form a tendril. If a B. subtilis strain produces surfactin at levels that can substantially weaken the overall water surface tension of the colony, water floods the agar surface in a thin layer, within which bacteria swarm and migrate rapidly. This study sheds light on the role of water surface tension in regulating B. subtilis swarming, and provides insight into the mechanisms underlying swarming initiation and tendril formation.

No MeSH data available.


Related in: MedlinePlus

LC-MS of surfactin purified from strains 3610, F29-3, and FK955. (A) Strain 3610 was cultured in 50-ml LB broth; strains F29-3 and FK995 were cultured in 1 liter LB broth for 16 h. Surfactin in the culture supernatants was purified and analyzed by HPLC. Pure surfactin was used as a standard. (B) The HPLC peaks with retention times of 17.94 (strain 3610) and 17.97 (strain F29-3) were analyzed by MALDI-TOF mass spectrometry. The peaks with m/z 1030, 1044, 1058, and 1072, which correspond to the mass of [M + Na]+ ions of surfactin isoforms, are indicated. AU, Absorbance Unit.
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Figure 2: LC-MS of surfactin purified from strains 3610, F29-3, and FK955. (A) Strain 3610 was cultured in 50-ml LB broth; strains F29-3 and FK995 were cultured in 1 liter LB broth for 16 h. Surfactin in the culture supernatants was purified and analyzed by HPLC. Pure surfactin was used as a standard. (B) The HPLC peaks with retention times of 17.94 (strain 3610) and 17.97 (strain F29-3) were analyzed by MALDI-TOF mass spectrometry. The peaks with m/z 1030, 1044, 1058, and 1072, which correspond to the mass of [M + Na]+ ions of surfactin isoforms, are indicated. AU, Absorbance Unit.

Mentions: We analyzed 1 nanomole of surfactin (Sigma-Aldrich) by liquid chromatography to serve as a standard, and found that the pure compound yielded three peaks with retention times of 17.00, 17.25, and 17.92 min (Figure 2A). We also cultured strain 3610 in 50 ml LB broth for 16 h, precipitated surfactin from the culture supernatant under acidic (pH 2) conditions, and then extracted surfactin using dichloromethane (Al-Ajlani et al., 2007). Chromatographic analysis of the extract similarly revealed peaks at 17.00, 17.24, and 17.94 min (Figure 2A). We then purified surfactin from 1 liter of F29-3 culture supernatant, and liquid chromatography analysis revealed one peak with a retention time of 17.97 min (Figure 2A). A parallel experiment showed that a surfactin-synthesis mutant of F29-3, FK955, did not produce such a peak (Figure 2A). Surfactin concentration in the 3610 culture medium was estimated to be 5.6 μM, but only 3.2 × 10−4 μM in the F29-3 culture medium, which is 17,519-fold less than that produced by strain 3610 (Table 3). Analysis of the chromatographic peaks at the retention time of 17.9 min by MALDI-TOF mass spectrometry revealed peaks with m/z 1030, 1044, 1058, and 1072 (Figure 2B), which corresponds to the mass of [M + Na]+ ions of surfactin isoforms (Tang et al., 2010) and confirming that the chromatographic peaks are those of surfactin. In addition to surfactin, strain F29-3 is also known to produce fengycin, but fengycin appears to be unrelated to swarming (Luo et al., 2014).


Water surface tension modulates the swarming mechanics of Bacillus subtilis.

Ke WJ, Hsueh YH, Cheng YC, Wu CC, Liu ST - Front Microbiol (2015)

LC-MS of surfactin purified from strains 3610, F29-3, and FK955. (A) Strain 3610 was cultured in 50-ml LB broth; strains F29-3 and FK995 were cultured in 1 liter LB broth for 16 h. Surfactin in the culture supernatants was purified and analyzed by HPLC. Pure surfactin was used as a standard. (B) The HPLC peaks with retention times of 17.94 (strain 3610) and 17.97 (strain F29-3) were analyzed by MALDI-TOF mass spectrometry. The peaks with m/z 1030, 1044, 1058, and 1072, which correspond to the mass of [M + Na]+ ions of surfactin isoforms, are indicated. AU, Absorbance Unit.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4616241&req=5

Figure 2: LC-MS of surfactin purified from strains 3610, F29-3, and FK955. (A) Strain 3610 was cultured in 50-ml LB broth; strains F29-3 and FK995 were cultured in 1 liter LB broth for 16 h. Surfactin in the culture supernatants was purified and analyzed by HPLC. Pure surfactin was used as a standard. (B) The HPLC peaks with retention times of 17.94 (strain 3610) and 17.97 (strain F29-3) were analyzed by MALDI-TOF mass spectrometry. The peaks with m/z 1030, 1044, 1058, and 1072, which correspond to the mass of [M + Na]+ ions of surfactin isoforms, are indicated. AU, Absorbance Unit.
Mentions: We analyzed 1 nanomole of surfactin (Sigma-Aldrich) by liquid chromatography to serve as a standard, and found that the pure compound yielded three peaks with retention times of 17.00, 17.25, and 17.92 min (Figure 2A). We also cultured strain 3610 in 50 ml LB broth for 16 h, precipitated surfactin from the culture supernatant under acidic (pH 2) conditions, and then extracted surfactin using dichloromethane (Al-Ajlani et al., 2007). Chromatographic analysis of the extract similarly revealed peaks at 17.00, 17.24, and 17.94 min (Figure 2A). We then purified surfactin from 1 liter of F29-3 culture supernatant, and liquid chromatography analysis revealed one peak with a retention time of 17.97 min (Figure 2A). A parallel experiment showed that a surfactin-synthesis mutant of F29-3, FK955, did not produce such a peak (Figure 2A). Surfactin concentration in the 3610 culture medium was estimated to be 5.6 μM, but only 3.2 × 10−4 μM in the F29-3 culture medium, which is 17,519-fold less than that produced by strain 3610 (Table 3). Analysis of the chromatographic peaks at the retention time of 17.9 min by MALDI-TOF mass spectrometry revealed peaks with m/z 1030, 1044, 1058, and 1072 (Figure 2B), which corresponds to the mass of [M + Na]+ ions of surfactin isoforms (Tang et al., 2010) and confirming that the chromatographic peaks are those of surfactin. In addition to surfactin, strain F29-3 is also known to produce fengycin, but fengycin appears to be unrelated to swarming (Luo et al., 2014).

Bottom Line: Many Bacillus subtilis strains swarm, often forming colonies with tendrils on agar medium.It is known that B. subtilis swarming requires flagella and a biosurfactant, surfactin.B. subtilis colonies were found to contain water, and when a low amount of surfactin is produced, the water surface tension of the colony restricts expansion, causing bacterial density to rise.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Immunology, Chang Gung University Taoyuan, Taiwan ; Research Center for Bacterial Pathogenesis, Chang Gung University Taoyuan, Taiwan.

ABSTRACT
Many Bacillus subtilis strains swarm, often forming colonies with tendrils on agar medium. It is known that B. subtilis swarming requires flagella and a biosurfactant, surfactin. In this study, we find that water surface tension plays a role in swarming dynamics. B. subtilis colonies were found to contain water, and when a low amount of surfactin is produced, the water surface tension of the colony restricts expansion, causing bacterial density to rise. The increased density induces a quorum sensing response that leads to heightened production of surfactin, which then weakens water surface tension to allow colony expansion. When the barrier formed by water surface tension is breached at a specific location, a stream of bacteria swarms out of the colony to form a tendril. If a B. subtilis strain produces surfactin at levels that can substantially weaken the overall water surface tension of the colony, water floods the agar surface in a thin layer, within which bacteria swarm and migrate rapidly. This study sheds light on the role of water surface tension in regulating B. subtilis swarming, and provides insight into the mechanisms underlying swarming initiation and tendril formation.

No MeSH data available.


Related in: MedlinePlus