Multiple determinants influence root colonization and induction of induced systemic resistance by Pseudomonas chlororaphis O6

Colonization of the roots of tobacco by Pseudomonas chlororaphis O6 induces systemic resistance to the soft-rot pathogen, Erwinia carotovora ssp. carotovara SCC1. A screen of the transposon mutants of P. chlororaphis O6 showed mutants with about a fivefold reduction in ability to induce systemic resistance to the soft-rot disease. These mutations disrupted genes involved in diverse functions: a methyl-accepting chemotaxis protein, biosynthesis of purines, phospholipase C, transport of branched-chain amino acids and an ABC transporter. Additional mutations were detected in the intergenic spacer regions between genes encoding a GGDEF protein and fumarate dehydratase, and in genes of unknown function. The mutants in the ABC transporters did not display reduced root colonization. However, the other mutants had up to 100-fold reduced colonization levels. Generally the production of metabolites important for interactions in the rhizosphere, phenazines and siderophores, was not altered by the mutations. A reduced induction of systemic resistance by a purine biosynthesis mutant with a disrupted purM gene correlated with poor growth rate, lesser production of phenazines and siderophore and low levels of root colonization. These studies showed that multiple determinants are involved in the induction of systemic resistance, with there being a requirement for strong root colonization.     

Macrozoobenthos of two Antarctic glacial coves: a comparison with non-disturbed bottom areas

There are only few studies on shallow Antarctic benthic communities associated with habitats affected by intense mineral sedimentation inflow. The analysis of macrofaunal communities associated with two shallow, isolated glacial coves was performed in Admiralty Bay (King George Island) and compared with non-disturbed sites. Multivariate analyses (hierarchical classification, nMDS) clearly separated glacial cove communities (two assemblages) from the sites situated outside both basins (two assemblages). The community influenced by the streamflow of glacial discharge of meltwater situated in the area with sandy–clay–silt sediments had a very low species richness, diversity and abundance. It was dominated by eurytopic, motile deposit feeding polychaetes such as Mesospio moorei, Tharyx cincinnatus and Leitoscoloplos kerguelensis as well as the bivalve Yoldia eightsi. The second glacial community of the area located at a grater distance from the outlet of the stream was characterized by sandy–clay–silt and clay–silt deposits and showed also a low diversity and species richness. The most abundant here were peracarid crustaceans, with the dominant opportunistic feeder Cheirimedon femoratus. Community from the non-disturbed area with silty–clay–sand, and silty–sand sediments had higher species richness and diversity. The assemblage of fauna from the sandy bottom has values of those two indexes similar to those found in the disturbed areas.     

Design, synthesis and biological evaluation of 2-(substituted phenyl)thiazolidine-4-carboxylic acid derivatives as novel tyrosinase inhibitors

Herein we describe the design, synthesis and biological activities of 2-(substituted phenyl)thiazolidine-4-carboxylic acid derivatives as novel tyrosinase inhibitors. The target compounds 2a–2j were designed and synthesized from the structural characteristics of N-phenylthiourea, tyrosinase inhibitor and tyrosine, and l-DOPA, the natural substrates of tyrosinase. Among them, (2R/S,4R)-2-(2,4-dimethoxyphenyl)thiazolidine-4-carboxylic acid (2g) caused the greatest inhibition 66.47% at 20 μM of l-DOPA oxidase activity of mushroom tyrosinase. Kinetic analysis of tyrosinase inhibition revealed that 2g is a competitive inhibitor. We predicted the tertiary structure of tyrosinase, and simulated the docking of mushroom tyrosinase with 2g. These results suggest that the binding affinity of 2g with tyrosinase is high. Also, 2g effectively inhibited tyrosinase activity and reduced melanin levels in B16 cells treated with α-MSH. These data strongly suggest that 2g can suppress the production of melanin via the inhibition of tyrosinase activity.     

Agarose-gel-immobilized recombinant bacterial biosensors for simple and disposable on-site detection of phenolic compounds

In this study, recombinant bacterial biosensors were immobilized in an agarose matrix and used for the simple and disposable field monitoring of phenolic compounds. In brief, Escherichia coli cells harboring the pLZCapR plasmid, which was previously designed to express the β-galactosidase reporter gene in the presence of phenolic compounds, were immobilized in agarose gel with or without a substrate [chlorophenol red β-galactopyranoside (CPRG)] and dispensed to the wells of a 96-well plate. Analytes were added to the wells, and color development was monitored either directly from wells containing intact cells co-immobilized with CPRG (SYS I), or using cells that were lysed prior to the addition of CPRG (SYS L). SYS L showed relatively higher intensities and faster color development than SYS I. However, both systems developed a red color (representing hydrolysis of CPRG) in the presence of 10 μM to 10~100 mM phenol, with maximum responses seen at 1~5 and 50 mM phenol for SYS I and SYS L, respectively. Other phenolic compounds (2-chlorophenol, 2-methylphenol, 3-methylphenol, 4-chlorophenol, 2-nitrophenol, resorcinol, catechol, and 2,5-dimethylphenol) were also detected by the systems, with varied detection ranges and responses. The agarose-immobilized biosensors were stable for 28 days, retaining 39~69% of their activities when stored at 4°C without nutrients or additives. The immobilized biosensors described herein do not require the on-site addition of a substrate (in the case of SYS I), the pretreatment of samples, or the use of unwieldy instruments for the on-site monitoring of phenolic compounds from environmental samples.     

Genome sequence of the unclassified marine Gammaproteobacterium BDW918

The unclassified marine gammaproteobacterium BDW918, which utilizes volatile fatty acids but not most common carbohydrates and amino acids, was isolated from Dokdo seawater in South Korea. Here we present a draft genome of the strain BDW918, which encodes many putative genes related to fatty acid metabolism and aromatic hydrocarbon degradation.     

Apolipoprotein A-IV is a novel substrate for matrix metalloproteinases

Screening of matrix metalloproteinase (MMP)-14 substrates in human plasma using a proteomics approach previously identified apolipoprotein A-IV (apoA-IV) as a novel substrate for MMP-14. Here, we show that among the tested MMPs, purified apoA-IV is most susceptible to cleavage by MMP-7, and that apoA-IV in plasma can be cleaved more efficiently by MMP-7 than MMP-14. Purified recombinant apoA-IV (44-kDa) was cleaved by MMP-7 into several fragments of 41, 32, 29, 27, 24, 22 and 19 kDa. N-terminal sequencing of the fragments identified two internal cleavage sites for MMP-7 in the apoA-IV sequence, between Glu(185) and Leu(186), and between Glu(262) and Leu(263). The cleavage of lipid-bound apoA-IV by MMP-7 was less efficient than that of lipid-free apoA-IV. Further, MMP-7-mediated cleavage of apoA-IV resulted in a rapid loss of its intrinsic anti-oxidant activity. Based on the fact that apoA-IV plays important roles in lipid metabolism and possesses anti-oxidant activity, we suggest that cleavage of lipid-free apoA-IV by MMP-7 has pathological implications in the development of hyperlipidemia and atherosclerosis.