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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

Electron microscopy images of the P. aeruginosa strain PA14 WT from motility colonies on 0.5% agar or 0.4% mucin. P. aeruginosa bacteria were taken directly from the leading edge and center of the mucin-promoted surface motility zone (A and B) or the leading edge of the swarming motility zone (C). The cells were stained with 1% uranyl acetate and observed using a transmission electron microscope.
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fig5: Electron microscopy images of the P. aeruginosa strain PA14 WT from motility colonies on 0.5% agar or 0.4% mucin. P. aeruginosa bacteria were taken directly from the leading edge and center of the mucin-promoted surface motility zone (A and B) or the leading edge of the swarming motility zone (C). The cells were stained with 1% uranyl acetate and observed using a transmission electron microscope.

Mentions: We used transmission electron microscopy (TEM) to examine the morphology of P. aeruginosa strain PA14 taken from the edge and the center of the mucin-promoted surface motility zone. The method employed involved placing carbon-coated grids directly onto the surface of the motility colonies and then staining the cells with 1% uranyl acetate. The negatively stained cells were visualized using a TEM. As shown in Fig. 5A, the cells on the edge of the mucin-promoted surface motility zone were elongated compared to cells taken from the center of the motility zone. Measurement of the lengths of 10 to 15 random bacteria in each of 4 different squares of a carbon-coated grid placed on the middle or edge of the motility colony revealed that, on average, the length of the bacterial cells from the edge was 1.4- ± 0.2-fold greater than the length of the cells in the middle. Differences in flagellation were also clearly observed: at the edge of the motility zone, the majority of bacteria lacked flagella, with only 9 out of 60 bacterial cells assessed in 4 random grids having flagella, while at the middle, 47 out of 60 cells were flagellated (Fig. 5B). Moreover, while cells taken from swarming tendrils were highly organized (i.e., cells were aligned one next to another in the same direction as the moving tendril), the orientation of bacterial cells taken from the edge of the mucin-promoted surface motility zone was apparently random, with cells overlaying each other (Fig. 5C).


Mucin promotes rapid surface motility in Pseudomonas aeruginosa.

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

Electron microscopy images of the P. aeruginosa strain PA14 WT from motility colonies on 0.5% agar or 0.4% mucin. P. aeruginosa bacteria were taken directly from the leading edge and center of the mucin-promoted surface motility zone (A and B) or the leading edge of the swarming motility zone (C). The cells were stained with 1% uranyl acetate and observed using a transmission electron microscope.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig5: Electron microscopy images of the P. aeruginosa strain PA14 WT from motility colonies on 0.5% agar or 0.4% mucin. P. aeruginosa bacteria were taken directly from the leading edge and center of the mucin-promoted surface motility zone (A and B) or the leading edge of the swarming motility zone (C). The cells were stained with 1% uranyl acetate and observed using a transmission electron microscope.
Mentions: We used transmission electron microscopy (TEM) to examine the morphology of P. aeruginosa strain PA14 taken from the edge and the center of the mucin-promoted surface motility zone. The method employed involved placing carbon-coated grids directly onto the surface of the motility colonies and then staining the cells with 1% uranyl acetate. The negatively stained cells were visualized using a TEM. As shown in Fig. 5A, the cells on the edge of the mucin-promoted surface motility zone were elongated compared to cells taken from the center of the motility zone. Measurement of the lengths of 10 to 15 random bacteria in each of 4 different squares of a carbon-coated grid placed on the middle or edge of the motility colony revealed that, on average, the length of the bacterial cells from the edge was 1.4- ± 0.2-fold greater than the length of the cells in the middle. Differences in flagellation were also clearly observed: at the edge of the motility zone, the majority of bacteria lacked flagella, with only 9 out of 60 bacterial cells assessed in 4 random grids having flagella, while at the middle, 47 out of 60 cells were flagellated (Fig. 5B). Moreover, while cells taken from swarming tendrils were highly organized (i.e., cells were aligned one next to another in the same direction as the moving tendril), the orientation of bacterial cells taken from the edge of the mucin-promoted surface motility zone was apparently random, with cells overlaying each other (Fig. 5C).

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