Pigment variations induced by the oxygen level of the medium in a marine bacterium alteromonas sp. (strain cect 4800)

Abstract

A red-pigmented bacterial strain was isolated from indoor cultures of the marine microalga Tetraselmis suecica Butcher (Prasynophyceae) and identified as belonging to the genus Alteromonas (strain CECT 4800). Pigment composition was analyzed by means of high-performance liquid chromatography (HPLC), and spectral characteristics of three major pigments with reddish and yellowish colorations were determined. Changes in pigment composition during growth in liquid medium containing either ferric citrate, sodium citrate, glucose or glucose plus iron, as well as in relation to the oxygen concentration in the liquid medium were investigated. Pigment production was found to be enhanced with culture aging, the highest enhancement occurring in iron-deprived cultures. An increase in the major pigment (a red pigment) content of 70% in relation to the initial one took place when a culture fed with ferric citrate was bubbled with molecular oxygen. In contrast, red pigment content decreased to about 50% of the initial content when the culture was sparged with nitrogen. Other pigments did not exhibit substantial modifications. Increase in the red pigment content was also observed after the different cultures were exposed to diverse oxygen concentrations for one hour. Similar results were obtained in cultures submitted to both strong aeration and agitation (5 mL min^–1 air and 500 rpm, respectively). Findings of this study suggest that pigment production by Alteromonas sp. (strain CECT 4800), in particular that of the red pigment, could rely on the oxygen concentration in the culture medium due to antioxidative reactions.