Manganese acquisition is facilitated by PilA in the cyanobacterium Synechocystis sp. PCC 6803.

Jacob J Lamb,Martin F Hohmann-Marriott

doi:10.1371/journal.pone.0184685

Abstract

Manganese is an essential element required by cyanobacteria, as it is an essential part of the oxygen-evolving center of photosystem II. In the presence of atmospheric oxygen, manganese is present as manganese oxides, which have low solubility and consequently provide low bioavailability. It is unknown if cyanobacteria are able to utilize these manganese sources, and what mechanisms may be employed to do so. Recent evidence suggests that type IV pili in non-photosynthetic bacteria facilitate electron donation to extracellular electron acceptors, thereby enabling metal acquisition. Our present study investigates whether PilA1 (major pilin protein of type IV pili) enables the cyanobacterium Synechocystis PCC 6808 to access to Mn from manganese oxides. We present physiological and spectroscopic data, which indicate that the presence of PilA1 enhances the ability of cyanobacteria to grow on manganese oxides. These observations suggest a role of PilA1-containing pili in cyanobacterial manganese acquisition.

Highlights

Cyanobacteria have fundamentally changed our planet [1]. Oxygen, which these organisms produce, complexes with transition metals, thereby limiting metal bioavailability [2,3,4]. One such metal is Mn, which cyanobacteria require in larger quantity than other bacteria [5], as it is an essential co-factor for the catalysis of photosynthetic water splitting
The molecular machinery for uptake of soluble Mn2+ has be described [6, 7], but whether and how Mn from Mn oxides can be accessed by cyanobacteria is unknown
Several biological mechanisms have been implicated for accessing iron, another oxidized transition metal, crucial for photosynthetic electron transport

Summary

Introduction

Cyanobacteria have fundamentally changed our planet [1] Oxygen, which these organisms produce, complexes with transition metals, thereby limiting metal bioavailability [2,3,4]. One such metal is Mn, which cyanobacteria require in larger quantity than other bacteria [5], as it is an essential co-factor for the catalysis of photosynthetic water splitting. The molecular machinery for uptake of soluble Mn2+ has be described [6, 7], but whether and how Mn from Mn oxides can be accessed by cyanobacteria is unknown. Several biological mechanisms have been implicated for accessing iron, another oxidized transition metal, crucial for photosynthetic electron transport. There remains uncertainty concerning the molecular components that are involved in reductive iron uptake

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Conclusion