Brown algae (Phaeophyceae) are complex photosynthetic organisms with a very different evolutionary history to green plants, to which they are only distantly related(1). These seaweeds are the dominant species in rocky coastal ecosystems and they exhibit many interesting adaptations to these, often harsh, environments. Brown algae are also one of only a small number of eukaryotic lineages that have evolved complex multicellularity (Fig. 1). We report the 214 million base pair (Mbp) genome sequence of the filamentous seaweed Ectocarpus siliculosus (Dillwyn) Lyngbye, a model organism for brown algae(2-5), closely related to the kelps(6,7) (Fig. 1). Genome features such as the presence of an extended set of light-harvesting and pigment biosynthesis genes and new metabolic processes such as halide metabolism help explain the ability of this organism to cope with the highly variable tidal environment. The evolution of multicellularity in this lineage is correlated with the presence of a rich array of signal transduction genes. Of particular interest is the presence of a family of receptor kinases, as the independent evolution of related molecules has been linked with the emergence of multicellularity in both the animal and green plant lineages. The Ectocarpus genome sequence represents an important step towards developing this organism as a model species, providing the possibility to combine genomic and genetic(2) approaches to explore these and other(4,5) aspects of brown algal biology further

SummaryRx in potato encodes a protein with a nucleotide binding site (NBS) and leucine-rich repeats (LRR) that confers resistance against Potato virus X. The NBS and LRR domains in Rx are present in many disease resistance proteins in plants and in regulators of apoptosis in animals. To investigate structure-function relationships of NBS-LRR proteins we exploited the potential of Rx to mediate a cell death response. With wild-type Rx cell death is elicited only in the presence of the viral coat protein. However, following random mutagenesis of Rx, we identified mutants in which cell death is activated in the absence of viral coat protein.Out of 2500 Rx clones tested there were seven constitutive gain-of-function mutants carrying eight independent mutations. The mutations encoded changes in the LRR or in conserved RNBS-D and MHD motifs of the NBS. Based on these findings we propose that there are inhibitory domains in the NBS and LRR. The constitutive gain-of-function phenotypes would be due to deletion or modification of these inhibitory domains. However activation of Rx is not simply release of negative regulation by the LRR and adjacent sequence because deleted forms of Rx that lack constitutive gain of function mutations are not active unless the protein is overexpressed.

Following a single blind, cross-over and non-randomized design we investigated the effect of 7-day use of chlorhexidine (CHX) mouthwash on the salivary microbiome as well as several saliva and plasma biomarkers in 36 healthy individuals. They rinsed their mouth (for 1 min) twice a day for seven days with a placebo mouthwash and then repeated this protocol with CHX mouthwash for a further seven days. Saliva and blood samples were taken at the end of each treatment to analyse the abundance and diversity of oral bacteria, and pH, lactate, glucose, nitrate and nitrite concentrations. CHX significantly increased the abundance of Firmicutes and Proteobacteria, and reduced the content of Bacteroidetes, TM7, SR1 and Fusobacteria. This shift was associated with a significant decrease in saliva pH and buffering capacity, accompanied by an increase in saliva lactate and glucose levels. Lower saliva and plasma nitrite concentrations were found after using CHX, followed by a trend of increased systolic blood pressure. Overall, this study demonstrates that mouthwash containing CHX is associated with a major shift in the salivary microbiome, leading to more acidic conditions and lower nitrite availability in healthy individuals.Chlorhexidine (CHX) has been commonly used in dental practice as antiseptic agent since 1970, due to its long-lasting antibacterial activity with a broad-spectrum of action 1 . Since then, many clinical trials have shown effective results of CHX for the clinical management of dental plaque and gingival inflammation and bleeding 2-4 . This is supported by other studies using in vitro methods and reporting positive results of CHX in reducing the proliferation of bacterial species associated with periodontal disease, such as Enterobacteria, Porphyromonas gingivalis, Fusobacterium nucleatum, as well as different species of Actinomyces and Streptococcus, including Streptococcus mutans, which is considered the main etiological agent of dental caries 4,5 . Other studies have also reported that the use of CHX was effective in the treatment of halitosis, especially in reducing the levels of halitosis-related bacteria colonising the dorsal surface of the tongue 6 .The anti-microbial activity of CHX however, has been extensively studied using in vitro culture methods, which limit the identification and cultivation of all microorganisms in the environment 4 . To the best of our knowledge, only one recent study has investigated the effect of CHX mouthwash on mixed bacterial communities (microbiome) of the tongue using new genome sequencing techniques such as 16 S rRNA 7 . The study found differences in over 10 different species colonizing the tongue, and a lower microbial diversity after using CHX for a week, but did not analyse other parameters related to oral health such as pH, lactate production or buffering capacity 7 . Additionally, we and others have recently shown that the use of CHX in healthy subjects can attenuate the nitrate-reducing activity of oral bacteria by at least 80% 8-11 . This in turn leads to lo...