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Stenotrophomonas maltophilia WR-C is capable of forming biofilm on polystyrene and glass. The lipopolysaccharide/exopolysaccharide-coupled biosynthetic genes rmlA, rmlC, and xanB are necessary for biofilm formation and twitching motility. Mutants with mutations in rmlAC and xanB display contrasting biofilm phenotypes on polystyrene and glass and differ in swimming motility.Microorganisms can develop biofilms or clogging mats, causing the failure of septic tanks, systems for on-site wastewater disposal. If water in these clogged systems were contaminated by pathogens, it would pose a threat to human health. We isolated Stenotrophomonas maltophilia strain WR-C from a clogged septic tank system that consistently formed biofilms on sand grains, produced exopolysaccharides (EPS), and caused clogging in sand columns (33). S. maltophilia is a gram-negative, rod-shaped, and obligate aerobic bacterium with polar flagella in the ␥-␤ subdivision of Proteobacteria (3,14). It is found in various environments and recently has emerged as an important human pathogen. Very little is known about the mechanisms of biofilm formation by S. maltophilia. It has been shown to adhere to HEp-2 cells as well as abiotic surfaces, such as plastic, glass, and Teflon (7-10, 16).To identify genes that are involved in biofilm formation by S. maltophilia WR-C, about 4,500 transposon mutants generated with the EZ::TN Ͻ R6K␥ori/KAN-2 Ͼ Tnp transposome (Epicenter, Madison, Wis.) were screened for defects in biofilm formation in 96-well polystyrene plates (Becton-Dickinson Labware, Franklin Lakes, N.J.) by using a modified microtiter plate assay (11,29). Briefly, wells containing 200 l Trypticase soy (TS) broth were inoculated with overnight cultures and incubated at 30°C, 50 rpm for 2 days. Biofilm cells were stained with 0.1% crystal violet and washed, the stain remaining in the cells was solubilized with 70% ethanol, and the optical density at 590 nm was determined. Three mutants, TPH7, TPH11, and TPH13, whose growth was similar to that of the wild type but which were deficient in biofilm formation, were selected for further characterization.The transposon flanking regions were rescued by "rescue cloning" as described by the manufacturer and sequenced by using the primers KAN-2 FP-1 and R6KAN-2 RP-1 (Table 1). The transposon-inserted genes are homologous to three genes involved in the biosynthesis of nucleotide sugar precursors of lipopolysaccharide (LPS) and EPS in Xanthomonas campestris pv. campestris ATCC 33913 (GenBank accession no. AE008922) (6). The genes are rmlC (for TPH7, 74% identity), rmlA (for TPH11, 78% identity), and xanB (for TPH13, 80% identity), which are located in the rml and xan operons of X. campestris pv. campestris (19,20). As no genome sequence is available and the gene cluster involved in LPS/EPS biosynthesis has not been reported for S. maltophilia, the DNA segments flanking the transposon in TPH7, TPH11, and TPH13 were sequenced. The complete sequences of the rmlBACD and xanAB operons and their flanking genes were deter...

An increasing incidence of diagnosed type 2 diabetes was observed for each sex in most age groups in Taiwan, but was most marked in the youngest age group. A parallel increase in obesity was observed with the increasing incidence of diabetes.

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SummaryA major challenge of modern agricultural biotechnology is the optimization of plant architecture for enhanced productivity, stress tolerance and water use efficiency (WUE). To optimize plant height and tillering that directly link to grain yield in cereals and are known to be tightly regulated by gibberellins (GAs), we attenuated the endogenous levels of GAs in rice via its degradation. GA 2‐oxidase (GA2ox) is a key enzyme that inactivates endogenous GAs and their precursors. We identified three conserved domains in a unique class of C20 GA2ox, GA2ox6, which is known to regulate the architecture and function of rice plants. We mutated nine specific amino acids in these conserved domains and observed a gradient of effects on plant height. Ectopic expression of some of these GA2ox6 mutants moderately lowered GA levels and reprogrammed transcriptional networks, leading to reduced plant height, more productive tillers, expanded root system, higher WUE and photosynthesis rate, and elevated abiotic and biotic stress tolerance in transgenic rice. Combinations of these beneficial traits conferred not only drought and disease tolerance but also increased grain yield by 10–30% in field trials. Our studies hold the promise of manipulating GA levels to substantially improve plant architecture, stress tolerance and grain yield in rice and possibly in other major crops.