Hydroxamic acid present in Rhodotorula pilimanae cultures grown at low pH and its metabolic relation to rhodotorulic acid

Abstract

Rhodotorula pilimanae CBS 4479, when grown at pH 2.8 in iron-limited media, produced rhodotorulic acid and a second hydroxamic acid which was characterized as 1hydroxy-3(S)-amino-2-piperidone (HAP). The latter, which was not converted to rhodotorulic acid, was shown to arise from cyclization of -yV-hydroxyornithine. The addition of iron to growing cultures effected a parallel depression of have previously reviewed the features of rhodotorulic acid which render it the substance of choice for biosynthetic studies in the siderochrome (iron transport compound) series (Akers et a!., 1972). Rhodotorulic acid was thought to arise from --hydroxyornithine (OHOrn)1; however, due to the instability of OHOrn at pH values above the hydroxylamine pKlx of 5.5 we were reluctant to examine this compound as a precursor. In an attempt to overcome this problem we adapted Rhodotorula pilimanae to grow at pH 2.8. A hydroxamic acid produced at this pH differed from rhodotorulic acid in that it was retained by a cation exchange resin.This paper deals with the purification, characterization by comparison with synthetic material, and origin of 1-hydroxy-3(S)-amino-2-piperidone (HAP). The results indicate that at low pH OHOrn, a direct precursor of rhodotorulic acid, is diverted into the medium where it is cyclized nonenzymatically to HAP. Materials and MethodsR. pilimanae cultures adapted to low pH were maintained as liquid cultures on low pH ASKP medium (see below). Crystalline rhodotorulic acid was obtained from low-iron cultures of R. pilimanae (Atkin and Neilands, 1968). OHOrn was from HC1 hydrolysates of rhodotorulic acid (Atkin and Neilands, 1968).5-lV-Acetyl-5-/V-hydroxyornithine (AcOHOrn) was synthesized from OHOrn (Akers et al., 1972).Medium. R. pilimanae was cultured for 10-14 days at 30°o n a rotary shaker in the ASKP medium previously described (Akers et a!., 1972). The pH was adjusted to 2.8 • 0.1 using concentrated H3P04. Iron (as ferric ammonium sulfate)was not added unless specifically stated.Hydroxamates were determined spectrophotometrically (Atkin and Neilands, 1968). A tetrazolium spray was used for the detection of hydroxylamines (Snow, 1954

Cellular organization of siderophore biosynthesis in Pseudomonas aeruginosa: Evidence for siderosomes

“…A similar distribution had been observed for wild-type PvdA [44] and is consistent with the presence at the N-terminus of the enzyme of a hydrophobic, inner-membrane-anchoring domain [24,44]. This it is a highly unstable compound [47] so must be promptly sequestered and used by the PVDI biosynthesis machinery once synthesized by PvdA and PvdF. The presence of PvdA in this siderosome allows hydroxy-ornithine to be synthesized close to the PVDI-assembling machinery.…”

Membrane-association determinants of the ω-amino acid monooxygenase PvdA, a pyoverdine biosynthetic enzyme from Pseudomonas aeruginosa

“…To the best of our knowledge, in P. aeruginosa, OHOrn is exclusively utilized for pyoverdine biosynthesis. Moreover, because of its high instability at neutral pH (Akers & Neilands, 1973), cytoplasmic OHOrn should promptly be formylated and/ or sequestered into the nascent pyoverdine backbone by the pyoverdine biosynthesis machinery. In this scenario, our work provides the basis for future studies aimed at investigating the subcellular localization of the whole pyoverdine biosynthesis machinery.…”

Growth of T-Strain Mycoplasmas in Medium Without Added Urea: Effect of Trace Amounts of Urea and of a Urease Inhibitor

“…The hydroxamic acids have been shown to have no growth-inhibiting effect on a number of bacterial species both with and without urease activity, but they do inhibit bacterial ureases (6). High concentrations (0.1%, wt/vol) of sorbic hydroxamic acid are effective inhibitors of fungi which are not ureolytic (3), and hydroxamic acids also play a role in iron chelation in the respiration of some organisms (1). The iron levels of growth media are, in turn, of considerable importance for the growth of some fungi (4).…”