Restoring the complete

medium again caused the oxygen concentration to fall. The same behavior was observed in a duplicate experiment. These experiments show that oxygen and glucose utilization are interdependent. Heterogeneous patterns of protein synthetic activity in biofilms The induction of a GFP has been used to reveal regions of active protein synthesis in biofilms [12–14]. When this technique was applied to P. aeruginosa biofilms grown in drip-flow reactors, a stratified pattern of activity was observed (Figure 2). Expression of GFP was localized in a band at the top of the biofilm adjacent to the source of nutrients and oxygen. The dimension of the GFP-expressing zone averaged 66 ± 30 μm (n = 3, ± SD). The average thickness of the entire biofilm was 170 ± 78 μm (n = 3, ± SD) (Table 1). While the predominant zone of activity was along the air interface (Figure 2A), IPI-549 mw GFP fluorescence was occasionally observed in thin strata in the interior and even at the bottom of the biofilm (Figure 2B). The observation of fluorescent GFP at the bottom of the biofilm argues against the interpretation that these patterns are an artifact of incomplete IPTG penetration. MK-1775 in vivo In prior studies, the facile penetration

of IPTG throughout P. aeruginosa biofilms has been demonstrated [12, 14]. Figure 2 Spatial pattern of protein synthetic activity, as revealed by transient expression of an inducible GFP (green) in a P. aeruginosa biofilm grown in a drip-flow reactor. In this frozen section, the steel substratum was formerly at the bottom and the DNA Damage inhibitor aerated nutrient medium at the top. Rhodamine B counterstaining (red) indicates the extent of

the biofilm. Table 1 Determination of mean biofilm thickness and mean dimension Mannose-binding protein-associated serine protease of the zone in which GFP was expressed. Strain (plasmid) IPTG (mM) Biofilm*† Thickness (μm ± SD) GFP zone*† dimension (μm ± SD) Maximum† Fluorescence intensity (arbitrary ± SD) PAO1 (pAB1) 0 165 ± 100 none 24 ± 26 PAO1 (pAB1) 1 170 ± 78 66 ± 30 166 ± 61 PAO1 (pMF54) 1 120 ± 38 none 3 ± 1 *The thickness of the area of GFP expression as well as the overall thickness of the biofilm was measured 3 times. Measurement of Pseudomonas aeruginosa PAO1 carrying plasmid pAB1 containing an IPTG-inducible GFP with and without IPTG are compared with P. aeruginosa carrying plasmid pMF54 lacking GFP. †The uncertainties indicated are standard deviations. Transcriptional profiling of biofilms – nutritional and growth status The RNA was extracted from 3-day old P. aeruginosa drip-flow reactor grown biofilms and subjected to global transcriptional profiling. These microarray data have been deposited to Gene Expression Omnibus (GEO) accession GSE22164.