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Mucin promotes rapid surface motility in Pseudomonas aeruginosa.

Yeung AT, Parayno A, Hancock RE - MBio (2012)

Bottom Line: In this study, we added mucin to swimming media and found that it promoted the ability of P. aeruginosa to exhibit rapid surface motility.Interestingly, bacterial cells at the thick edge appeared piled up and lacked flagella, while cells at the motility center had flagella.Our data from various genetic and phenotypic studies suggest that mucin may be promoting a modified form of swarming or a novel form of surface motility in P. aeruginosa.

View Article: PubMed Central - PubMed

Affiliation: Centre for Microbial Diseases and Immunity Research, University of British Columbia, Vancouver, British Columbia, Canada.

ABSTRACT

Unlabelled: An important environmental factor that determines the mode of motility adopted by Pseudomonas aeruginosa is the viscosity of the medium, often provided by adjusting agar concentrations in vitro. However, the viscous gel-like property of the mucus layer that overlays epithelial surfaces is largely due to the glycoprotein mucin. P. aeruginosa is known to swim within 0.3% (wt/vol) agar and swarm on the surface at 0.5% (wt/vol) agar with amino acids as a weak nitrogen source. When physiological concentrations or as little as 0.05% (wt/vol) mucin was added to the swimming agar, in addition to swimming, P. aeruginosa was observed to undergo highly accelerated motility on the surface of the agar. The surface motility colonies in the presence of mucin appeared to be circular, with a bright green center surrounded by a thicker white edge. While intact flagella were required for the surface motility in the presence of mucin, type IV pili and rhamnolipid production were not. Replacement of mucin with other wetting agents indicated that the lubricant properties of mucin might contribute to the surface motility. Based on studies with mutants, the quorum-sensing systems (las and rhl) and the orphan autoinducer receptor QscR played important roles in this form of surface motility. Transcriptional analysis of cells taken from the motility zone revealed the upregulation of genes involved in virulence and resistance. Based on these results, we suggest that mucin may be promoting a new or highly modified form of surface motility, which we propose should be termed "surfing."

Importance: An important factor that dictates the mode of motility adopted by P. aeruginosa is the viscosity of the medium, often provided by adjusting agar concentrations in vitro. However, the gel-like properties of the mucous layers that overlay epithelial surfaces, such as those of the lung, a major site of Pseudomonas infection, are contributed mostly by the production of the glycoprotein mucin. In this study, we added mucin to swimming media and found that it promoted the ability of P. aeruginosa to exhibit rapid surface motility. These motility colonies appeared in a circular form, with a bright green center surrounded by a thicker white edge. Interestingly, bacterial cells at the thick edge appeared piled up and lacked flagella, while cells at the motility center had flagella. Our data from various genetic and phenotypic studies suggest that mucin may be promoting a modified form of swarming or a novel form of surface motility in P. aeruginosa.

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Related in: MedlinePlus

Surface propagation of P. aeruginosa strain PA14 WT on wetting or viscosity-enhancing agents. Cultures of P. aeruginosa bacteria were spotted onto MSCFM plates with 0.3% (wt/vol) agar and various concentrations of (A) Tween 80 or (B) CMC. Images were taken after incubation at 37°C for 13 h.
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fig8: Surface propagation of P. aeruginosa strain PA14 WT on wetting or viscosity-enhancing agents. Cultures of P. aeruginosa bacteria were spotted onto MSCFM plates with 0.3% (wt/vol) agar and various concentrations of (A) Tween 80 or (B) CMC. Images were taken after incubation at 37°C for 13 h.

Mentions: As described above, rhamnolipid production was not required for this form of surface motility on mucin plates. This led us to suspect that mucin might be serving as a surrogate for a surfactant to reduce surface tension and promote this form of motility. It has been demonstrated that soluble mucin is both viscous and lubricative (25, 26). For example, the addition of porcine gastric mucin enhances the viscosity and wettability of solutions (27). Basically, the viscosity-enhancing property of mucin allows mucin to bind water, reducing the free water content in the environment and thus increasing the ability of bacteria to slide across the surface. To examine whether the lubricant/wetting properties of mucin affected the surface motility, we replaced mucin with various wetting agents. Replacement of mucin with Tween 20 promoted rapid surface propagation of P. aeruginosa (Fig. 8A). The replacement of mucin with Tween 20 did not result in a pattern identical to that of mucin and gave surface motility patterns that were more inconsistent, with variable levels of surface coverage seen in different trials, while the edges of the Tween 20-mediated motility colony were thinner than the rest of the motility colony, in contrast to the consistent surface coverage and thick edges of mucin-mediated motility zones. We also demonstrated that flagellar mutants were able to spread on Tween-containing plates (data not shown). These results were consistent with the suggestion that the improved surface wetness provided by mucin facilitated the ability of bacterial cells to expand on the agar. We also replaced mucin with carboxymethyl cellulose (CMC), which has both lubricative and viscous properties, to examine its effect on surface motility. As shown in Fig. 8B, CMC promoted surface propagation but higher concentrations of CMC were required compared to mucin. At 1% (wt/vol), CMC promoted only about 50% of the surface coverage promoted by 0.4% (wt/vol) mucin. Overall, it was concluded that a unique combination of wetness and viscosity conferred by mucin likely contributed to its effects on surface motility.


Mucin promotes rapid surface motility in Pseudomonas aeruginosa.

Yeung AT, Parayno A, Hancock RE - MBio (2012)

Surface propagation of P. aeruginosa strain PA14 WT on wetting or viscosity-enhancing agents. Cultures of P. aeruginosa bacteria were spotted onto MSCFM plates with 0.3% (wt/vol) agar and various concentrations of (A) Tween 80 or (B) CMC. Images were taken after incubation at 37°C for 13 h.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3569861&req=5

fig8: Surface propagation of P. aeruginosa strain PA14 WT on wetting or viscosity-enhancing agents. Cultures of P. aeruginosa bacteria were spotted onto MSCFM plates with 0.3% (wt/vol) agar and various concentrations of (A) Tween 80 or (B) CMC. Images were taken after incubation at 37°C for 13 h.
Mentions: As described above, rhamnolipid production was not required for this form of surface motility on mucin plates. This led us to suspect that mucin might be serving as a surrogate for a surfactant to reduce surface tension and promote this form of motility. It has been demonstrated that soluble mucin is both viscous and lubricative (25, 26). For example, the addition of porcine gastric mucin enhances the viscosity and wettability of solutions (27). Basically, the viscosity-enhancing property of mucin allows mucin to bind water, reducing the free water content in the environment and thus increasing the ability of bacteria to slide across the surface. To examine whether the lubricant/wetting properties of mucin affected the surface motility, we replaced mucin with various wetting agents. Replacement of mucin with Tween 20 promoted rapid surface propagation of P. aeruginosa (Fig. 8A). The replacement of mucin with Tween 20 did not result in a pattern identical to that of mucin and gave surface motility patterns that were more inconsistent, with variable levels of surface coverage seen in different trials, while the edges of the Tween 20-mediated motility colony were thinner than the rest of the motility colony, in contrast to the consistent surface coverage and thick edges of mucin-mediated motility zones. We also demonstrated that flagellar mutants were able to spread on Tween-containing plates (data not shown). These results were consistent with the suggestion that the improved surface wetness provided by mucin facilitated the ability of bacterial cells to expand on the agar. We also replaced mucin with carboxymethyl cellulose (CMC), which has both lubricative and viscous properties, to examine its effect on surface motility. As shown in Fig. 8B, CMC promoted surface propagation but higher concentrations of CMC were required compared to mucin. At 1% (wt/vol), CMC promoted only about 50% of the surface coverage promoted by 0.4% (wt/vol) mucin. Overall, it was concluded that a unique combination of wetness and viscosity conferred by mucin likely contributed to its effects on surface motility.

Bottom Line: In this study, we added mucin to swimming media and found that it promoted the ability of P. aeruginosa to exhibit rapid surface motility.Interestingly, bacterial cells at the thick edge appeared piled up and lacked flagella, while cells at the motility center had flagella.Our data from various genetic and phenotypic studies suggest that mucin may be promoting a modified form of swarming or a novel form of surface motility in P. aeruginosa.

View Article: PubMed Central - PubMed

Affiliation: Centre for Microbial Diseases and Immunity Research, University of British Columbia, Vancouver, British Columbia, Canada.

ABSTRACT

Unlabelled: An important environmental factor that determines the mode of motility adopted by Pseudomonas aeruginosa is the viscosity of the medium, often provided by adjusting agar concentrations in vitro. However, the viscous gel-like property of the mucus layer that overlays epithelial surfaces is largely due to the glycoprotein mucin. P. aeruginosa is known to swim within 0.3% (wt/vol) agar and swarm on the surface at 0.5% (wt/vol) agar with amino acids as a weak nitrogen source. When physiological concentrations or as little as 0.05% (wt/vol) mucin was added to the swimming agar, in addition to swimming, P. aeruginosa was observed to undergo highly accelerated motility on the surface of the agar. The surface motility colonies in the presence of mucin appeared to be circular, with a bright green center surrounded by a thicker white edge. While intact flagella were required for the surface motility in the presence of mucin, type IV pili and rhamnolipid production were not. Replacement of mucin with other wetting agents indicated that the lubricant properties of mucin might contribute to the surface motility. Based on studies with mutants, the quorum-sensing systems (las and rhl) and the orphan autoinducer receptor QscR played important roles in this form of surface motility. Transcriptional analysis of cells taken from the motility zone revealed the upregulation of genes involved in virulence and resistance. Based on these results, we suggest that mucin may be promoting a new or highly modified form of surface motility, which we propose should be termed "surfing."

Importance: An important factor that dictates the mode of motility adopted by P. aeruginosa is the viscosity of the medium, often provided by adjusting agar concentrations in vitro. However, the gel-like properties of the mucous layers that overlay epithelial surfaces, such as those of the lung, a major site of Pseudomonas infection, are contributed mostly by the production of the glycoprotein mucin. In this study, we added mucin to swimming media and found that it promoted the ability of P. aeruginosa to exhibit rapid surface motility. These motility colonies appeared in a circular form, with a bright green center surrounded by a thicker white edge. Interestingly, bacterial cells at the thick edge appeared piled up and lacked flagella, while cells at the motility center had flagella. Our data from various genetic and phenotypic studies suggest that mucin may be promoting a modified form of swarming or a novel form of surface motility in P. aeruginosa.

Show MeSH
Related in: MedlinePlus