Isolation and characterization of Bacillus subtilis genes involved in siderophore biosynthesis: relationship between B. subtilis sfpo and Escherichia coli entD genes

Abstract

In response to iron deprivation, Bacillus subtilis secretes a catecholic siderophore, 2,3-dihydroxybenzoyl glycine, which is similar to the precursor of the Escherichia coli siderophore enterobactin. We isolated two sets of B. subtilis DNA sequences that complemented the mutations of several E. coli siderophore-deficient (ent) mutants with defective enterobactin biosynthesis enzymes. One set contained DNA sequences that complemented only an entD mutation. The second set contained DNA sequences that complemented various combinations of entB, entE, entC, and entA mutations. The two sets of DNA sequences did not appear to overlap. AB. subtilis mutant containing an insertion in the region of the entD homolog grew much more poorly in low-iron medium and with markedly different kinetics. These data indicate that (i) at least five of the siderophore biosynthesis genes of B. subtilis can function in E. coli, (ii) the genetic organization of these siderophore genes in B. subtilis is similar to that in E. coli, and (iii) the B. subtilis entD homolog is required for efficient growth in low-iron medium. The nucleotide sequence of the B. subtilis DNA contained in plasmid pENTA22, a clone expressing the B. subtilis entD homolog, revealed the presence of at least two genes. One gene was identified as sfpo, a previously reported gene involved in the production of surfactin in B. subtilis and which is highly homologous to the E. coli entD gene. We present evidence that the E. coli entD and B. subtilis sfpo genes are interchangeable and that their products are members of a new family of proteins which function in the secretion of peptide molecules.

The pobA gene of Burkholderia cenocepacia encodes a Group I Sfp-type phosphopantetheinyltransferase required for biosynthesis of the siderophores ornibactin and pyochelin

“…As expected, expression of entD in AN90 in trans resulted in the restoration of siderophore production, yielding a phenotype identical to that of JM83. The same result was observed for the heterologous PPTase gene sfp, as reported elsewhere (Grossman et al, 1993). Moreover, pobA was also able to substitute for entD in the complementation assay (Fig.…”

“…PPTases are also required for the activation of NRPSs and polyketide synthetases (PKSs) that participate in the biosynthesis of compounds other than siderophores Sieber & Marahiel, 2003). For example, the Bacillus subtilis PPTase Sfp is required for the biosynthesis of surfactin, a cyclic lipopeptide possessing antibiotic properties, as well as for the catecholate siderophore bacillibactin (Nakano et al, 1992;Grossman et al, 1993;Quadri et al, 1998b;Heerklotz & Seelig, 2001;May et al, 2001). PPTases such as EntD and Sfp, which play roles in secondary metabolism, are referred to as Sfp-type PPTases, and several different Sfp-type PPTases may be encoded by the same bacterium (Lu et al, 2008).…”

Identification of iron-regulated genes of Bifidobacterium breve UCC2003 as a basis for controlled gene expression

“…Furthermore, a homolog of EfeU and part of the transport system are found in the surfactin siderophore cluster of the Gram-positive organism B. subtilis, which is responsible for high-affinity ferric iron uptake. 29 A feature of all OFeT proteins is the occurrence of two REXXE amino acid residue motifs. 27,30 On examination of the BfeU amino acid sequence two corresponding REGLE motifs were identified (Fig.…”

Induction of surfactin production in Bacillus subtilis by gsp, a gene located upstream of the gramicidin S operon in Bacillus brevis

“…Enterobactin production is induced under iron deprivation and enables the cell by binding ferric ions to grow under low-iron conditions (6). The possible involvement of Sfpo in the secretion of the B. subtilis siderophore 2,3-dihydroxybenzoyl glycine was reported recently by Grossman et al (8).…”

“…Gsp shows 34% identity and 52% similarity to the sfp gene product. Sequence similarity of Gsp not only to the Sfp protein but also to EntD, a protein involved in the last step in synthesis of the siderophore enterobactin in Escherichia coli, was observed (8). Enterobactin production is induced under iron deprivation and enables the cell by binding ferric ions to grow under low-iron conditions (6).…”