Characterization of Hydrogen Metabolism in the Multicellular Green Alga Volvox carteri.

Adam J Cornish,Saundra Mason,Katrin Gärtner,Eric L Hegg,Robin Green,James G Umen

doi:10.1371/journal.pone.0125324

Abstract

Hydrogen gas functions as a key component in the metabolism of a wide variety of microorganisms, often acting as either a fermentative end-product or an energy source. The number of organisms reported to utilize hydrogen continues to grow, contributing to and expanding our knowledge of biological hydrogen processes. Here we demonstrate that Volvox carteri f. nagariensis, a multicellular green alga with differentiated cells, evolves H2 both when supplied with an abiotic electron donor and under physiological conditions. The genome of Volvox carteri contains two genes encoding putative [FeFe]-hydrogenases (HYDA1 and HYDA2), and the transcripts for these genes accumulate under anaerobic conditions. The HYDA1 and HYDA2 gene products were cloned, expressed, and purified, and both are functional [FeFe]-hydrogenases. Additionally, within the genome the HYDA1 and HYDA2 genes cluster with two putative genes which encode hydrogenase maturation proteins. This gene cluster resembles operon-like structures found within bacterial genomes and may provide further insight into evolutionary relationships between bacterial and algal [FeFe]-hydrogenase genes.

Highlights

Hydrogen is an essential component in the metabolism of a variety of microorganisms [1,2,3]
V. carteri is closely related to C. reinhardtii, a green alga with well-described hydrogen metabolism [28,29]
A variety of green algae have been characterized for their ability to couple energy derived from photosynthesis to the production of H2, especially the model organism C. reinhardtii [15,30,50]

Summary

Introduction

Hydrogen is an essential component in the metabolism of a variety of microorganisms [1,2,3]. Two putative [FeFe]-hydrogenase genes were annotated in the genome of V. carteri [31], which may provide the organism with H2 metabolism similar to that of C. reinhardtii. Genes coding for the functional hydrogenases and associated maturation factors are arranged in a unique operon-like gene cluster within the V. carteri genome, providing additional evidence for an evolutionary relationship between bacterial and green algal [FeFe]-hydrogenases.

Results

Conclusion