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.
Highlights
Molecular oxygen is the main product released by algae during photosynthetic activity, and consumption by associated bacteria of this photosynthetically produced oxygen has been proposed as an important factor in regulating
The bacterium used in this study was identified as belonging to the genus Alteromonas (Alteromonas sp., strain CECT 4800) (González-del Valle, 1997), and was isolated from cultures of the marine microalgae Tetraselmis suecica (Prasynophyceae), which was obtained from the Microalga Culture Collection of the Instituto de Ciencias Marinas de Andalucía (CSIC, Cádiz, Spain)
Bacterial cell density was achieved by determining the number of colony formation units (CFU), according to the methodology described by Buck (1979)
Summary
INTRODUCCIÓNEvidence exists on associations between algal and bacterial populations in both natural environments and cultures (Caldwell, 1977; Jones, 1982; Paerl and Pinckney, 1996) and the interactions involved in those associations have been shown to be mainly assimilation by bacteria of organic compounds released by algae (Bell, 1983), while bacteria might supply CO2 to algae (Marshall, 1989). It has been found that a number of algae grow in bacteria-contaminated cultures better than in axenic ones (Berland et al, 1970; Fitzsimons and Smith, 1984; Tranvik, 1990; Sundh, 1992). Se ha comprobado que un gran número de algas crecen mejor en cultivos contaminados con bacterias que en cultivos axénicos (Berland et al, 1979; Fitzsimons y Smith, 1984; Tranvik, 1990; Sundh, 1992). At higher rates of photosynthesis, oxygen could result harmful for the associated bacteria as well
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