Taking these data together we suggest that an integron associated cassette product participates in some

aspect of cell metabolism that directly or indirectly impacts on growth such that a secondary BI 2536 mutation(s) is required to maintain viability or growth. This product must be encoded by one of the genes located in Torin 1 cost cassettes 8 to 15 inclusive since the smaller deletion encompassing cassettes 16-60 does not display any of these effects (Figure 2). Figure 4 Comparison of V. rotiferianus DAT722-Sm (A) and mutants d8-60a (B), d8-60b (C) and d8-60c (D) streaked on LB20 agar. The d8-60 mutants show the presence of microcolonies on the streak line. Cassette deletions change the outermembrane protein profiles of cells Porins play a major role in controlling the permeability of the outermembrane of Gram-negative bacteria. Changes in porin composition affect the cell’s osmotic balance and nutrient transport [21]. Therefore, it was hypothesized that the likely osmotic shock of d8-60a in 2M + pyruvate and the growth defects of d8-60b and d8-60c in 2M + glucose might be due to changes in the

composition of outermembrane porins. Outermembrane protein profiles showed significant changes in the composition of porins in all three d8-60 click here mutants compared to the wild-type using different growth media indicating an inability of these mutants to regulate their porins normally (Figure 5A, B and 5C). In 2M + glucose conditions, d8-60a showed slight decreases in four proteins identified as VapA (the structural subunit of a two-dimensional lattice in the outer membrane called the S-layer; band 1), maltoporin (band 2), OmpU porin (band 3) and an OmpU-like porin (band 4) compared to the wild-type, consistent with the healthy growth of d8-60a in this medium (Figure 5A). However, the changes in regulation of porins in CYTH4 d8-60a was clearly observed when grown in 2M + LB nutrients as it showed increased amounts of VapA (band 1) and maltoporin (band 2) and the presence of a putative porin (band 4) not detected in the wild-type under these nutrient conditions (Figure 5C). This irregular

regulation explained the inability for d8-60a to grow in 2M salts without the presence of an osmoprotectant such as glycine-betaine or glucose to restore the osmotic balance. Figure 5 Outermembrane protein (OMP) analysis of V. rotiferianus DAT722-Sm (wt) and d8-60 mutants grown in 2M + glucose (A), 2M + pyruvate (B) and 2M + LB nutrients (C). Labelled proteins in C were identified as 1) VapA, 2) Maltoporin, 3) OmpU porin, 4) putative porin and 5) OmpU-like porin as indicated in the Table below the panels. The molecular weight marker is given in the left most lane for panels A/B, C and D/E/F with the relevant sizes (in kDa) given left of the respective panels. The mutants d8-60b and d8-60c had very similar porin profiles, a result consistent with the similar growth phenotypes displayed by these mutants.