Engineering Plant-Microbe Symbiosis for Rhizoremediation of Heavy Metals

The use of plants for rehabilitation of heavy-metal-contaminated environments is an emerging area of interest because it provides an ecologically sound and safe method for restoration and remediation. Although a number of plant species are capable of hyperaccumulation of heavy metals, the technology is not applicable for remediating sites with multiple contaminants. A clever solution is to combine the advantages of microbe-plant symbiosis within the plant rhizosphere into an effective cleanup technology. We demonstrated that expression of a metal-binding peptide (EC20) in a rhizobacterium, Pseudomonas putida 06909, not only improved cadmium binding but also alleviated the cellular toxicity of cadmium. More importantly, inoculation of sunflower roots with the engineered rhizobacterium resulted in a marked decrease in cadmium phytotoxicity and a 40% increase in cadmium accumulation in the plant root. Owing to the significantly improved growth characteristics of both the rhizobacterium and plant, the use of EC20-expressing P. putida endowed with organic-degrading capabilities may be a promising strategy to remediate mixed organic-metal-contaminated sites.     

Gastrointestinal microflora,food components and colon cancer prevention

Evidence that the intestinal microbiota is intrinsically linked with overall health, including cancer risk, is emerging. Moreover, its composition is not fixed but can be influenced by several dietary components. Dietary modifiers, including the consumption of live bacteria (probiotics) and indigestible or limited digestible food constituents such as oligosaccharides (prebiotics) and polyphenols or both (synbiotics), are recognized modifiers of the numbers and types of microbes and have been reported to reduce colon cancer risk experimentally. Microorganisms also have the ability to generate bioactive compounds from food components. Examples include equol from isoflavones, enterodiol and enterolactone from lignans and urolithins from ellagic acid, which have also been demonstrated to retard experimentally induced cancers. The gastrointestinal microbiota can also influence both sides of the energy balance equation, namely, as a factor influencing energy utilization from the diet and as a factor that influences host genes that regulate energy expenditure and storage. Because of the link between obesity and cancer incidence and mortality, this complex complexion deserves greater attention. Overall, a dynamic interrelationship exists between the intestinal microbiota and colon cancer risk, which can be modified by dietary components and eating behaviors.     

Genome Sequence and Comparative Genomics Analysis of a Vibrio cholerae O1 Strain Isolated from a Cholera Patient in Malaysia

The genome sequence analysis of a clinical Vibrio cholerae VC35 strain from an outbreak case in Malaysia indicates multiple genes involved in host adaptation and a novel Na⁺-driven multidrug efflux pump-coding gene in the genome of Vibrio cholerae with the highest similarity to VMA_001754 of Vibrio mimicus VMA223.     

Maresin Biosynthesis and Identification of Maresin 2, a New Anti-Inflammatory and Pro-Resolving Mediator from Human Macrophages

Maresins are a new family of anti-inflammatory and pro-resolving lipid mediators biosynthesized from docosahexaenoic acid (DHA) by macrophages. Here we identified a novel pro-resolving product, 13R,14S-dihydroxy-docosahexaenoic acid (13R,14S-diHDHA), produced by human macrophages. PCR mapping of 12-lipoxygenase (12-LOX) mRNA sequence in human macrophages and platelet showed that they are identical. This human 12-LOX mRNA and enzyme are expressed in monocyte-derived cell lineage, and enzyme expression levels increase with maturation to macrophages or dendritic cells. Recombinant human 12-LOX gave essentially equivalent catalytic efficiency (k_cat/K_M) with arachidonic acid (AA) and DHA as substrates. Lipid mediator metabololipidomics demonstrated that human macrophages produce a novel bioactive product 13,14-dihydroxy-docosahexaenoic acid in addition to maresin-1, 7R,14S-dihydroxy-4Z,8E,10E,12Z,16Z,19Z-docosahexaenoic acid (MaR1). Co-incubations with human recombinant 12-LOX and soluble epoxide hydrolase (sEH) demonstrated that biosynthesis of 13,14-dihydroxy-docosahexaenoic acid (13,14-diHDHA) involves the 13S,14S-epoxy-maresin intermediate produced from DHA by 12-LOX, followed by conversion via soluble epoxide hydrolase (sEH). This new 13,14-diHDHA displayed potent anti-inflammatory and pro-resolving actions, and at 1 ng reduced neutrophil infiltration in mouse peritonitis by ∼40% and at 10 pM enhanced human macrophage phagocytosis of zymosan by ∼90%. However, MaR1 proved more potent than the 13R,14S-diHDHA at enhancing efferocytosis with human macrophages. Taken together, the present findings demonstrate that macrophages produced a novel bioactive product identified in the maresin metabolome as 13R,14S-dihydroxy-docosahexaenoic acid, from DHA via conversion by human 12-LOX followed by sEH. Given its potent bioactions, we coined 13R,14S-diHDHA maresin 2 (MaR2).     

A taxonomy of transcriptomic cell types across the isocortex and hippocampal formation

1. Download : Download high-res image (239KB)
2. Download : Download full-size image

     

Streamlining 'search and destroy': cost-effective surveillance for invasive species management

Invasive species surveillance has typically been targeted to where the species is most likely to occur. However, spatially varying environmental characteristics and land uses may affect more than just the probability of occurrence. Biodiversity or economic value, and the ease of detection and control are also likely to vary. We incorporate these factors into a detection and treatment model of a low-density invader to determine the surveillance strategy that minimizes expected management costs. Sites with a high probability of invader occurrence and great benefits associated with detection warrant intensive surveillance; however, the optimum investment is a nonlinear function of these factors. Environments where the invader is relatively easy to detect are prioritized for surveillance, although only a moderate investment is necessary to ensure a high probability of detection. Intensive surveillance effort may be allocated to other sites if the probability of occurrence, budget and/or expected benefits is sufficiently high.