A reverse transcriptase PCR (RT-PCR) assay was developed for the detection of acute bee paralysis virus (ABPV) and black queen cell virus (BQCV), two honeybee viruses. Complete genome sequences were used to design unique PCR primers within a 1-kb region from the 3 end of both genomes to amplify a fragment of 900 bp from ABPV and 700 bp from BQCV. The combined guanidinium thiocyanate and silica membrane method was used to extract total RNA from samples of healthy and laboratory-infected bee pupae. In a blind test, RT-PCR successfully identified the samples containing ABPV and BQCV. Sensitivities were approximately 1,600 genome equivalents of purified ABPV and 130 genome equivalents of BQCV.

The complete genome sequence of acute bee paralysis virus (ABPV) was determined. The 9470 nucleotide, polyadenylated RNA genome encoded two open reading frames (ORF1 and ORF2), which were separated by 184 nucleotides. The deduced amino acid sequence of the 5' ORF1 (nucleotides 605 to 6325) showed significant similarity to the RNA-dependent RNA polymerase, helicase, and protease domains of viruses from the picornavirus, comovirus, calicivirus, and sequivirus families, as well as to a novel group of insect-infecting RNA viruses. The 3' ORF2 (nucleotides 6509-9253) was proposed as encoding a capsid polyprotein with three major structural proteins (35, 33, and 24 kDa) and a minor protein (9.4 kDa). This was confirmed by N-terminal sequence analysis of two of these proteins. The overall genome structure of ABPV showed similarities to those of Drosophila C virus, Plautia stali intestine virus, Rhopalosiphum padi virus, and Himetobi P virus, which have been classified into a novel group of picorna-like insect-infecting RNA viruses called cricket paralysis-like viruses. It is suggested that ABPV belongs to the cricket paralysis-like viruses.

A virus with picorna-like biophysical properties was isolated from South African honey bees. On the basis of serology, it was identified as an isolate of black queen-cell virus (BQCV). Nucleotide sequence analysis revealed an 8550 nt polyadenylated genome containing two large ORFs. The 5h-proximal ORF (ORF 1) represented 4968 nt while the 3h-proximal ORF (ORF 2) represented 2562 nt. The ORFs were separated by a 208 nt intergenic region and were flanked by a 657 nt 5h-untranslated region and a 155 nt 3h-untranslated region. Deduced amino acid sequences for ORF 1 and ORF 2 were most similar to the non-structural and structural proteins, respectively, of Drosophila C virus (DCV), Rhopalosiphum padi virus (RhPV), Himetobi P virus (HiPV) and Plautia stali intestine virus (PSIV). It is proposed that BQCV belongs to the group of picorna-like, insectinfecting RNA viruses constituted by DCV, RhPV, HiPV and PSIV.

The sucrose operon of Clostridium beijerinckii NCIMB 8052 comprises four genes, which encode a sucrose-specific enzyme IIBCSV protein of the phosphotransferase system (ScrA), a transcriptional repressor (ScrR), a sucrose hydrolase (ScrB) and an ATP-dependent fructokinase (ScrK). The scrARBK operon was cloned in Escherichia coli in three stages. Initial isolation was achieved by screening a C. beijerinckii genomic library in E. coli for clones able to utilize sucrose, while the remainder of the operon was isolated by inverse PCR and by plasmid rescue of flanking regions from a scrB mutant constructed by targeted gene disruption. Substrate specificity assays confirmed that the sucrose hydrolase was a /I-fructofuranosidase, able to hydrolyse sucrose and raffinose but not inulin or levans, and that the scrK gene encoded an ATP/Mg2+-dependent fructokinase. Both enzyme activities were induced by sucrose in C. beijerinckii. Disruption of the scr operon of C. beijerinckii by targeted plasmid integration into either the scrR or the scrB gene resulted in strains unable to utilize sucrose, indicating that this was the only inducible sucrose catabolic pathway in this organism. RNA analysis confirmed that the genes of the scr operon were co-transcribed on a 5 kb mRNA transcript and that transcription was induced by sucrose, but not by glucose, fructose, maltose or xylose. Primer extension experiments identified the transcriptional start site as lying 44 bp upstream of the scrA ATG start codon, immediately adjacent to the imperfect palindrome sequence proposed to be a repressor binding site. Disruption of the scrR gene resulted in constitutive transcription of the upstream scrA gene, suggesting that scrR encodes a transcriptional repressor which acts a t the scrA operator sequence. The scrR gene is therefore itself negatively autoregulated as part of the polycistronic scrARBK mRNA.

The South African isolate of Black queen-cell virus (BQCV), a honey bee virus, was previously found to have an 8550 nucleotide genome excluding the poly(A) tail. Its genome contained two ORFs, a 5h-proximal ORF encoding a putative replicase protein and a 3h-proximal ORF encoding a capsid polyprotein. Long reverse transcription (RT)-PCR was used to produce infectious transcripts for BQCV and to manipulate its genome. Primers were designed for the amplification of the complete genome, the in vitro transcription of infectious RNA and PCR-directed mutagenesis. An 18-mer antisense primer was designed for RT to produce full-length single-stranded cDNA (ss cDNA). Unpurified ss cDNA from the RT reaction mixture was used directly as a template to amplify the full genome by long high-fidelity PCR. The SP6 promoter sequence was introduced into the sense primer to transcribe RNA directly from the amplicon. RNA was transcribed in vitro with and without the presence of a cap analogue and injected directly into bee pupae, which were then incubated for 8 days. In vitro transcripts were infectious but the presence of a cap analogue did not increase the amount of virus recovered. A single base mutation abolishing an EcoRI restriction site was introduced by fusion-PCR, to distinguish viral particles recovered from infectious transcripts from wild-type virus (wtBQCV). Mutant virus (mutBQCV) and wtBQCV were indistinguishable by electron microscopy and Western blot analysis. The EcoRI restriction site was present in wtBQCV and not in mutBQCV. IntroductionBlack queen-cell virus (BQCV) was first isolated from queen larvae and pupae of honey bees found dead in their cells (Bailey & Woods, 1974). The name of the virus was derived from darkened areas on the walls of the cells containing infected pupae. BQCV has been shown to be the most common cause of death of queen larvae in Australia (Anderson, 1993). The virus is also often present in bees infested with the microsporidian parasite Nosema apis (Allen & Ball, 1996 ;Bailey et al., 1983) and may be implicated in the mortality of bees infected with this parasite.The interest in viruses as honey bee pathogens has often been academic, with many viruses persisting as inapparent infections. More recently, increasing knowledge of the interactions between honey bee viruses and parasites, notably the mite Varroa destructor, has led to suggestions that they may be involved in honey bee mortality (Bailey et al., 1983 ;Ball & Allen, 1988 ;Allen & Ball, 1996 ;Brødsgaard et al., 2000). This relationship between mite infestation and virus infection is not clearly understood. The term ' bee parasitic mite syndrome ' has been used to describe a disease complex in which colonies are simultaneously infested with mites and infected with viruses and have a high mortality (Shimanuki et al., 1994). Although the mite has been demonstrated to act as an activator of inapparent virus infections and as a virus-transmitting vector (Ball & Allen, 1988 ;Bowen-Walker et al., 1999), no direct link between the actual mit...