Physiological aspects of carbon monoxide production by the brown alga Nereocystis luetkeana

Abstract

The pneumatocyst gases of those members of the Phaeophyta which possess single, large pneumatocysts (Nereocystis sp., Pelagophycus spp., and Eklonia spp.) contain CO. Although CO is produced by a number of algae, internal retention is unique to the above-mentioned genera. This study was undertaken to examine the physiological aspects of CO origin and retention in pneumatocysts of Nereocystis. A new hypothesis to explain this phenomenon consists of three parts: firstly, that CO production is a by-product of autolytic cell metabolism which is linked to respiration by a requirement for energy, probably in the form of ATP: secondly, the occurrence of CO in the pneumatocysts of large kelps is the result of autolytic processes that are active in pneumatocyst formation; and thirdly, CO concentrations in the pneumatocyst are determined by the production rate and loss rate by diffusion into the surrounding environment through the pneumatocyst wall. The CO-producing pathway has a heat-labile component which indicates enzyme involvement in production.The presence of a CO- and CN-sensitive electron-transport system is shown, although the existence of cytochrome a–a3 could not be demonstrated. Sufficient CO production can be obtained after homogenization and fractionation to permit further biochemical investigation.