Identification of major zinc-binding proteins from a marine cyanobacterium: insight into metal uptake in oligotrophic environments

Abstract

Marine cyanobacteria make a significant contribution to primary production whilst occupying some of the most nutrient poor regions of the world's oceans. The low bioavailability of trace metals can limit the growth of phytoplankton in ocean waters, but only scarce data are available on the requirements of marine microbes for zinc. Recent genome mining studies suggest that marine cyanobacteria have both uptake systems for zinc and proteins that utilize zinc as a cofactor. In this study, the oligotrophic strain Synechococcus sp. WH8102 was grown at different zinc concentrations. Using metalloproteomics approaches, we demonstrate that even though this organism's growth was not affected by extremely low zinc levels, cells accumulated significant quantities of zinc, which was shown to be protein-associated by 2D liquid chromatography and ICP-MS. This indicates that the mechanisms for zinc uptake in Synechococcus sp. WH8102 are extremely efficient. Significantly, expression of SYNW2224, a putative porin, was up-regulated during growth in zinc-depleted conditions. Furthermore, along with 30 other proteins, SYNW2224 was captured by immobilised zinc affinity chromatography, indicating the presence of surface-exposed site(s) with metal-binding capacity. It is proposed that this porin plays a role in high-affinity zinc uptake in this and other cyanobacteria.

Recyclable and Intrinsically Anti‐cyanobacterial Polyanionic Membranes

“…The presence of Zn 2+ may block the phycobilisome and promote the depolymerization of the phycobilisome, which affects the photosynthesis capability and chlorophyll‐a, and inhibits the growth of the cyanobacteria. In addition, Zn 2+ may affect the activity of alkaline phosphatase, and cause the malabsorption of algal cells to organic phosphorus . Among the PA‐M membranes studied, PA‐Fe membrane exhibits the highest anti‐cyanobacterial activities.…”

Zinc Homeostasis at the Bacteria/Host Interface—From Coordination Chemistry to Nutritional Immunity

“…In the outer membrane, there are porins, also called channels, which are responsible for passive transport, for example, metal ions and small molecules across the outer membrane . The OM porins may permit both uptake and efflux . The expression of several genes encoding outer membrane porins of Pseudomonas protegens (OprD family porins) was affected by zinc concentration in the growth medium …”

“…Acinetobacter baumannii encodes two TonB‐ExbB‐ExbD systems. One of them is under the transcriptional control of Zur, based on the presence of a Zur‐binding consensus sequence within the tonB promoter …”

Microbial Metalloproteomics

“…A disadvantage of this approach is the dilution of the sample and the large datasets that are obtained and have to be analyzed. LC protein separation combined with ICP-MS metal analysis has been used successfully for the analysis of different microbial metalloproteomes [11,15,23]. Two particularly interesting examples are described in Section 3.1 and Section 3.2.…”

“…The metalloproteomes of several bacteria and archaea have been studied in significant detail [10,11,12,13,14,15,16]. Major metalloproteomic methods are presented, important research findings that have been obtained from metalloproteomics research are discussed, and finally, an outlook is given on emerging approaches that may propel this field in the near future.…”