Metabolic relation of cyanobacteria to aromatic compounds

Abstract

Cyanobacteria, also known as blue-green (micro)algae, are able to sustain many types of chemical stress because of metabolic adaptations that allow them to survive and successfully compete in a variety of ecosystems, including polluted ones. As photoautotrophic bacteria, these microorganisms synthesize aromatic amino acids, which are precursors for a large variety of substances that contain aromatic ring(s) and that are naturally formed in the cells of these organisms. Hence, the transformation of aromatic secondary metabolites by cyanobacteria is the result of the possession of a suitable "enzymatic apparatus" to carry out the biosynthesis of these compounds according to cellular requirements. Another crucial aspect that should be evaluated using varied criteria is the response of cyanobacteria to the presence of extracellular aromatic compounds. Some aspects of the relationship between aromatic compounds and cyanobacteria such as the biosynthesis of aromatic compounds, the influence of aromatic compounds on these organisms and the fate of aromatic substances inside microalgal cells are presented in this paper. The search for this information has suggested that there is a lack of knowledge about the regulation of the biosynthesis of aromatic substances and about the transport of these compounds into cyanobacterial cells. These aspects are of pivotal importance with regard to the biotransformation of aromatic compounds and understanding them may be the goals of future research.

Keywords: Aromatic compounds; Biotransformation; Cyanobacteria; Metabolic relations; Metabolic response.

Fig. 1

Biosynthesis of aromatic compounds by cyanobacteria based on cited literature

Fig. 2

An overview of the impact of aromatic compounds discussed in the text on the growth of cyanobacteria. The stimulatory or inhibitory effect was estimated on the basis of the average response of various strains of microalgae to the presence of xenobiotics. The values above the x-axis indicate growth stimulation, and the values below indicate growth suppression in the presence of chemicals. The neutral relationship is shown with dots

Fig. 3

Proposed pathways of the transformation of naphthalene by Oscillatoria sp.