Summary. White spot syndrome virus (WSSV) is type species of the genusWhispovirus of the new family Nimaviridae. Despite the elucidation of its genomic sequence, very little is known about the virus as only 6% of its ORFs show homology to known genes. One of the structural virion proteins, VP15, is part of the nucleocapsid of the virus and shows homology to some putative baculovirus DNA binding proteins. These DNA-binding or histone-like proteins are thought to be involved in the condensation and packaging of the genome in the nucleocapsid. Using bacterially expressed VP15 fusion proteins in ELISA and Far-Western experiments showed that VP15 interacts with itself, forming homomultimers, but not with the other major structural proteins of the WSSV virion. Antibodies against phosphorylated proteins revealed that VP15 originating from different sources was not phosphorylated. WSSV VP15 binds non-specifically to double-stranded DNA, but has a clear preference to supercoiled DNA suggesting that VP15 is involved in the packaging of the WSSV genome in the nucleocapsid. This research shed further light on the composition of WSSV virions and the function of one of its nucleocapsid proteins.

Neisseria meningitidis serogroup B is a pathogen that can infect diverse sites within the human host. According to the N. meningitidis genomic information and experimental observations, glucose can be completely catabolized through the Entner-Doudoroff pathway and the pentose phosphate pathway. The Embden-Meyerhof-Parnas pathway is not functional, because the gene for phosphofructokinase (PFK) is not present. The phylogenetic distribution of PFK indicates that in most obligate aerobic organisms, PFK is lacking. We conclude that this is because of the limited contribution of PFK to the energy supply in aerobically grown organisms in comparison with the energy generated through oxidative phosphorylation. Under anaerobic or microaerobic conditions, the available energy is limiting, and PFK provides an advantage, which explains the presence of PFK in many (facultatively) anaerobic organisms. In accordance with this, in silico flux balance analysis predicted an increase of biomass yield as a result of PFK expression. However, analysis of a genetically engineered N. meningitidis strain that expressed a heterologous PFK showed that the yield of biomass on substrate decreased in comparison with a pfkA-deficient control strain, which was associated mainly with an increase in CO 2 production, whereas production of by-products was similar in the two strains. This might explain why the pfkA gene has not been obtained by horizontal gene transfer, since it is initially unfavourable for biomass yield. No large effects related to heterologous expression of pfkA were observed in the transcriptome. Although our results suggest that introduction of PFK does not contribute to a more efficient strain in terms of biomass yield, achievement of a robust, optimal metabolic network that enables a higher growth rate or a higher biomass yield might be possible after adaptive evolution of the strain, which remains to be investigated.Abbreviations: dcw, dry cell weight; ED, Entner-Doudoroff; EMP, Embden-Meyerhof-Parnas; F6P, fructose 6-phosphate; FBA, flux balance analysis; FR, fold ratio; HGT, horizontal gene transfer; LP, linear programming; MCS, Monte Carlo simulation; NVI, Netherlands Vaccine Institute; PEP, phosphoenolpyruvate; PP, pentose phosphate, PTS system, phosphotransferase system. The microarray data discussed in this paper are available under GEO accession number GSE18951.Three supplementary tables, showing the relationships in bacterial species between PFK (encoded by pfkA), the glucose-specific PTS transporter EIIB Glc (encoded by ptsG) and glucokinase, GK (encoded by glk), are available with the online version of this paper. Additional data are also available with the online version of this paper in the form of the Excel file Additional data.xls, which includes six worksheets. The first worksheet, named 'model', contains the simplified metabolic model. The second worksheet, named 'abbreviations', contains a list of abbreviations of the metabolites. The third worksheet, named 'flux distributions', contains the calculated flux...