Cell density-dependent oligopeptide production in cyanobacterial strains

Abstract

Cyanobacteria can form blooms and in these situations they dominate the phytoplanktonic community, reaching extremely high densities. In the domain Bacteria, high population densities can stimulate a phenomenon known as quorum sensing, which may produce several modifications in the cell physiology. Very little is known about quorum sensing in Cyanobacteria. Because of their planktonic way of life, quorum sensing should be more evident during a bloom event. In this work, we tested whether cell density could shape the production of bioactive compounds produced by Cyanobacteria. The experiments consisted of two treatments, where cultures of Cyanobacteria were maintained at low and high cellular densities through a semi-continuous set-up. Analyses were performed by HPLC-PDA and MALDI-TOF MS. Seventeen peptides were detected and 14 identified, including microcystins, aeruginosins, cyanopeptolins and microviridins. The results showed that cellular density seems to have a significant effect on the peptides production. Most of the compounds had significantly higher cellular quotas in the higher-density treatment, although microviridins and an unknown peptide were produced only at low density. These results may hint at a possible role for quorum sensing in triggering the production of several cyanobacterial peptides.

Predicting microcystin concentrations in lakes and reservoirs at a continental scale: A new framework for modelling an important health risk factor

“…We suggest that at higher MC limits, where algal concentrations are much higher, UV penetration into the water column is greatly limited and this effect is much diminished. At this extreme, MC production may also increase several fold due to quorum sensing and stress from nutrient limitation (Pereira & Giani, 2014;Pimentel & Giani, 2014;Van de Waal et al, 2009;Wood et al, 2011).…”

Drivers of fluorescent dissolved organic matter in the global epipelagic ocean

“…In the surface ocean, we are likely observing the bulk of the recently produced tyrosine‐like materials that escape rapid microbial utilisation and the negative relationship with AOU would also be a consequence of the microbial utilization of a less recalcitrant fraction of the amino acid‐like substances. Similarly, the adverse conditions of the environment might be contributing to the inhibition of the exometabolites (e.g., peptides) released by bacteria typical of quorum sensing (Pereira and Giani ). This assumption, as well as the one that involves microbially produced humic‐like substances, is supported by a 72 h incubation experiment in the darkness where the amino acid‐like fluorescence decayed by 29% ± 9% and the marine humic‐like fluorescence increased by 20% ± 9% (Lønborg et al ).…”

Oligopeptides as Biomarkers of Cyanobacterial Subpopulations. Toward an Understanding of Their Biological Role

“…Whereas these studies report overall stability of peptide fingerprints, in some cases, nutrient limitation, high irradiance [80,81] and cyanobacterial cell densities [82] were observed to induce distortions in oligopeptide signatures of some strains of the genera Microcystis and Radiocystis . In particular, nutrient deprivation and high light resulted in the disappearance of minor microcystin variants ( i.e ., low intensity spectral signals) from the peptide fingerprints, presumably due to physiologically induced reductions in oligopeptide synthesis.…”

“…In particular, nutrient deprivation and high light resulted in the disappearance of minor microcystin variants ( i.e ., low intensity spectral signals) from the peptide fingerprints, presumably due to physiologically induced reductions in oligopeptide synthesis. Alternatively, several aeruginosin, cyanopeptolin, and microcystin variants could only be detected at high cell densities, remaining otherwise undetectable under low cell concentrations [82]. Difficulties in consistently detecting minor mass signals by MALDI-TOF MS had been reported earlier [56,83], although they were not interpreted in the context of the delimitation of chemotypes.…”

“…These variations, although minor, may turn out critical to detect minor peptides present at cellular concentrations close to analytical detection limits. In fact, peptides accounting for distortions in oligopeptide fingerprints are usually accompanied by one or more signals corresponding to major congeners of the same peptide class [80,81,82]. However, in the context of the definition of chemotypes, inconsistent detection of minor oligopeptides has to be treated with caution, especially when investigating chemotypes directly from natural populations.…”