Bacillus subtilisOperon Encoding a Membrane Receptor for Bacteriophage SPP1

Abstract

The results reported here have identified yueB as the essential gene involved in irreversible binding of bacteriophage SPP1 to Bacillus subtilis. First, a deletion in an SPP1-resistant (pha-2) strain, covering most of the yueB gene, could be complemented by a xylose-inducible copy of yueB inserted at amyE. Second, disruption of yueB by insertion of a pMutin4 derivative resulted in a phage resistance phenotype regardless of the presence or absence of IPTG (isopropyl-␤-D-thiogalactopyranoside). YueB homologues are widely distributed in grampositive bacteria. The protein Pip, which also serves as a phage receptor in Lactococcus lactis, belongs to the same family. yueB encodes a membrane protein of ϳ120 kDa, detected in immunoblots together with smaller forms that may be processed products arising from cleavage of its long extracellular domain. Insertional inactivation of yueB and the surrounding genes indicated that yueB is part of an operon which includes at least the upstream genes yukE, yukD, yukC, and yukBA. Disruption of each of the genes in the operon allowed efficient irreversible adsorption, provided that yueB expression was retained. Under these conditions, however, smaller plaques were produced, a phenotype which was particularly noticeable in yukE mutant strains. Interestingly, such reduction in plaque size was not correlated with a decreased adsorption rate. Overall, these results provide the first demonstration of a membrane-bound protein acting as a phage receptor in B. subtilis and suggest an additional involvement of the yukE operon in a step subsequent to irreversible adsorption.The interaction of a bacteriophage with the bacterial surface (adsorption) is the first step in the infection process. This step involves recognition of and binding to one or more cell envelope constituents and leads to ejection of the phage DNA from the capsid. It has long been appreciated that adsorption can proceed in two steps, one reversible step followed by irreversible commitment (1). Irreversible adsorption and ejection of DNA are possibly different descriptions of the same phenomenon, but this has not really been clarified. Similarly, DNA ejection from the capsid and injection into the cytoplasm are at best difficult to separate in vivo, except in those cases where injection itself proceeds in distinct phases, as in T5 (13).In the gram-negative world, several phage receptors have been identified, and in a number of cases (e.g., T4, T5, and T7 of Escherichia coli), the adsorption and injection processes are now beginning to be understood at a detailed molecular level (14,18,26). Much less is known about the first steps of infection for phages preying on gram-positive bacteria. Early work has established that glucosylated polyglycerol phosphate, the major and essential teichoic acid in Bacillus subtilis, serves as a receptor for several phages, including 29, 25, and SP01 (24,29,34,36). Mutations leading to a lack of glucosylation of this polymer block the phage adsorption process and plaque-forming ability. More rece...

EsxA and EsxB are secreted by an ESAT-6-like system that is required for the pathogenesis ofStaphylococcus aureusinfections

“…Recent sequence analysis revealed that yukA-yukB represents a single ORF (31). EssC, Rv3870, Rv3871, and YukA sequences encompass one or more FSDs (17).…”

Outer Membrane Proteins Ail and OmpF of Yersinia pestis Are Involved in the Adsorption of T7-Related Bacteriophage Yep-phi

“…This step involves the recognition of, and binding to, one or more cell envelope constituents, which leads to the ejection of the phage DNA from the capsid (17). The implementation of efficient phage therapies to target pathogenic bacteria requires detailed knowledge of the bacterial receptors recognized by the phages (18).…”

Virus Evolution toward Limited Dependence on Nonessential Functions of the Host: the Case of Bacteriophage SPP1

“…The observed SPP1 plaque phenotype could thus be due to a polar effect of the knockout on expression of downstream genes. Such an effect was previously reported for disruption of cistrons of the yuk operon, which encodes, in order, yukE, yukD, yukC, yukB, and yueB (32). To test this possibility, titrations of the mutant strains were carried out in the presence of 1 mM IPTG.…”

“…Phage infection was significantly affected in only seven singlegene knockout mutants. Five of these genes are part of the yuk operon, shown to be involved in SPP1 entry into the host cell cytoplasm (32). The other two genes are involved in protein synthesis and in proline catabolism.…”