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Center for Biofilm Engineering
Abstract:
"Stratified Growth in Pseudomonas aeruginosa Biofilms"
04-027 In this study, stratified patterns of protein synthesis and growth were
demonstrated in Pseudomonas aeruginosa biofilms. Spatial patterns of protein
synthetic activity inside biofilms were characterized by the use of two green
fluorescent protein (GFP) reporter gene constructs. One construct carried an
isopropyl-ß-D-thiogalactopyranoside (IPTG)-inducible gfpmut2 gene encoding a
stable GFP. The second construct carried a GFP derivative, gfp-AGA, encoding an
unstable GFP under the control of the growth-rate-dependent rrnBp1 promoter.
Both GFP reporters indicated that active protein synthesis was restricted to a
narrow band in the part of the biofilm adjacent to the source of oxygen. The
zone of active GFP expression was approximately 60 µm wide in colony biofilms
and 30 µm wide in flow cell biofilms. The region of the biofilm in which cells
were capable of elongation was mapped by treating colony biofilms with
carbenicillin, which blocks cell division, and then measuring individual cell
lengths by transmission electron microscopy. Cell elongation was localized at
the air interface of the biofilm. The heterogeneous anabolic patterns measured
inside these biofilms were likely a result of oxygen limitation in the biofilm.
Oxygen microelectrode measurements showed that oxygen only penetrated
approximately 50 µm into the biofilm. P. aeruginosa was incapable of anaerobic
growth in the medium used for this investigation. These results show that while
mature P. aeruginosa biofilms contain active, growing cells, they can also
harbor large numbers of cells that are inactive and not growing.
Werner, E., F. Roe, A. Bugnicourt, M.J. Franklin, A. Heydorn, S. Molin, B.
Pitts, and P.S. Stewart, "Stratified Growth in Pseudomonas aeruginosa Biofilms,"
Appl. Environ. Microbiol., 70(10):6188-6196 (2004) |
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