Isolation and characterization of arsenic-binding siderophores from Rhodococcus erythropolis S43: role of heterobactin B and other heterobactin variants

• Published in: Applied microbiology and biotechnology 2021-02, Vol.105 (4), p.1731-1744
• Main Authors: Retamal-Morales, Gerardo, Senges, Christoph Helmut Rudi, Stapf, Manuel, Olguín, Angel, Modak, Brenda, Bandow, Julia Elisabeth, Tischler, Dirk, Schlömann, Michael, Levicán, Gloria
• Format: Article
• Language: English
• Subjects: Actinomycetes; Arsenic; Arsenic compounds; Arsenite; Binding; Biomedical and Life Sciences; Biotechnology; Chelation; Chemical properties; Colorimetry; Depletion; Environmental aspects; Environmental Biotechnology; High-performance liquid chromatography; Identification and classification; Iron; Life Sciences; Liquid chromatography; Metabolites; Microbial Genetics and Genomics; Microbiology; moieties; NMR; Nuclear magnetic resonance; Ornithine; Physiological aspects; Rhodococcus; Rhodococcus erythropolis; Siderophores; Siderophores (Microbiology); Sodium arsenite; Soil contamination; Soil pollution; solid phase extraction; Solid phases; Structure
• ISSN: 0175-7598; 1432-0614
• DOI: 10.1007/s00253-021-11123-2

Rhodococcus erythropolis S43 is an arsenic-tolerant actinobacterium isolated from an arsenic contaminated soil. It has been shown to produce siderophores when exposed to iron-depleting conditions. In this work, strain S43 was shown to have the putative heterobactin production cluster htbABCDEFGHIJ(K) . To induce siderophore production, the strain was cultured in iron-depleted medium in presence and absence of sodium arsenite. The metabolites produced by S43 in the colorimetric CAS and As- m CAS assays, respectively, showed iron- and arsenic-binding properties reaching a chelating activity equivalent to 1.6 mM of desferroxamine B in the supernatant of the culture without arsenite. By solid-phase extraction and two subsequent HPLC separations from both cultures, several fractions were obtained, which contained CAS and As- m CAS activity and which were submitted to LC-MS analyses including fragmentation of the major peaks. The mixed-type siderophore heterobactin B occurred in all analyzed fractions, and the mass of the “Carrano heterobactin A” was detected as well. In addition, generation of a molecular network based on fragment spectra revealed the occurrence of several other compounds with heterobactin-like structures, among them a heterobactin B variant with an additional CH 2 O moiety. 1 H NMR analyses obtained for preparations from the first HPLC step showed signals of heterobactin B and of “Carrano heterobactin A” with different relative amounts in all three samples. In summary, our results reveal that in R. erythropolis S43, a pool of heterobactin variants is responsible for the iron- and arsenic-binding activities. Key points • Several heterobactin variants are the arsenic-binding compounds in Rhodococcus erythropolis S43. • Heterobactin B and the compound designated heterobactin A by Carrano are of importance. • In addition, other heterobactins with ornithine in the backbone exist, e.g., the new heterobactin C.