Whole cell microalgal-cyanobacterial array biosensor for monitoring Cd, Cr and Zn in aquatic systems

Bioavailable content of metals in aquatic systems has become critical in assessing the toxic effect of metals accumulating in the environment. Considering the need for rapid measurements, an optical microalgal-cyanobacterial array biosensor was developed using two strains of microalgae, Mesotaenium sp. and a strain of cyanobacteria Synechococcus sp. to detect Cd2+, Cr6+ and Zn2+ in aquatic systems. Microalgal and cyanobacterial cells were immobilized in a 96-well microplate using sol-gel method using silica. Optimum operational conditions for the biosensor array such as exposure time, storage stability, pH, and multiple metal effect were tested. A 10 min exposure time yielded optimum fluorescence values. Metal toxicity increased with decreasing pH, resulting in low relative fluorescence (%) and decreased with increasing pH, resulting in higher relative fluorescence (%). The optimum storage time for biosensor strains were 4 weeks for microalgal cultures and 8 weeks for cyanobacterial culture, at 4 °C storage temperature. The metal mixtures showed less effect on the inhibition of relative fluorescence (%) of microalgal/cyanobacterial cultures, displaying an antagonistic behavior among the metals tested. As a single unit, this photosynthetic array biosensor will be a valuable tool in detecting multi-metals in aquatic systems.

The Role of Selected Wavelengths of Light in the Activity of Photosystem II in Gloeobacter violaceus

Gloeobacter violaceus is a cyanobacteria species with a lack of thylakoids, while photosynthetic antennas, i.e., phycobilisomes (PBSs), photosystem II (PSII), and I (PSI), are located in the cytoplasmic membrane. We verified the hypothesis that blue–red (BR) light supplemented with a far-red (FR), ultraviolet A (UVA), and green (G) light can affect the photosynthetic electron transport chain in PSII and explain the differences in the growth of the G. violaceus culture. The cyanobacteria were cultured under different light conditions. The largest increase in G. violaceus biomass was observed only under BR + FR and BR + G light. Moreover, the shape of the G. violaceus cells was modified by the spectrum with the addition of G light. Furthermore, it was found that both the spectral composition of light and age of the cyanobacterial culture affect the different content of phycobiliproteins in the photosynthetic antennas (PBS). Most likely, in cells grown under light conditions with the addition of FR and G light, the average antenna size increased due to the inactivation of some reaction centers in PSII. Moreover, the role of PSI and gloeorhodopsin as supplementary sources of metabolic energy in the G. violaceus growth is discussed.

Prospects in Cadmium-Contaminated Water Management Using Free-Living Cyanobacteria (Oscillatoria sp.)

In this study, the removal of cadmium (Cd) by free-living Oscillatoria sp. was studied. Our results showed that maximal Cd removal efficiency (~60%) by the cyanobacterial culture was achieved within 12–24 h in the presence of 5.0 or 25.0 mg/L of Cd. The mechanisms underlying this phenomenon were explored by elemental analysis and FTIR-ATR spectroscopy. It was found that metal adsorption by negatively charged functional groups in the cyanobacterial biomass was the main mechanism used by Oscillatoria sp. to remove metal from the aqueous medium, followed by Cd bioaccumulation into living cells. Additionally, Cd-exposed microalgae showed increased oxidative stress (MDA formation), a decreased dehydrogenase activity, a higher amount of soluble carbohydrates and a decreased total carotenoid concentration, as compared to the control cells. These results suggest that Oscillatoria sp. improved its antioxidative defense system under stressful conditions, through carotenoid-mediated ROS quenching and induction of carbohydrate catabolism, in order to counteract the oxidative damage and preserve the photosynthetic machinery and cellular energetics. In fact, no significant reduction in Oscillatoria sp. cell density, total protein amount, and chlorophyll a content was observed after 24-h Cd exposure, even at the highest metal concentration tested (i.e., 25.0 mg/L). Hence, the presented results are the first to describe some new insights about the metabolic and physiological behavior of living Oscillatoria sp. during Cd remediation, and open up the possibility of finding an equilibrium that maximizes metal removal performance with an active cyanobacterial metabolism, to achieve a rewarding and sustainable management of industrial metal-polluted wastewater.

Draft Genome Sequence of Muricauda sp. Strain K001 Isolated from a Marine Cyanobacterial Culture

ABSTRACT We report the whole-genome sequence of Muricauda sp. strain K001 isolated from a marine cyanobacterial culture. This genome sequence will improve our understanding of the influence of heterotrophic bacteria on the physiology of cyanobacteria and may contribute to the development of new natural products.

First record of the soil cyanobacterium Nodosilinea epilithica (Synechococcales, Cyanobacteria) in Russia

Nodosilinea epilithica Perkerson et Casamatta is reported for the first time for Russia. The sample was isolated from a typical chestnut soil in the zone of dry steppes (Volgograd Region) and its identity was confirmed by morphological and molecular analyses. The specific feature of the studied strain is its ability to form nodules at normal (60–75 μmol photons ∙ m-2 ∙ sec-1) light. The number of nodules is supposed to be related to the age of a cyanobacterial culture.

Maribacter flavus sp. nov., isolated from a cyanobacterial culture pond

A Gram-stain-negative, yellow, non-spore-forming, strictly aerobic bacterium, designated C3T, was isolated from a cyanobacterial culture pond. Cells were halophilic, rod-shaped and able to move by gliding. Growth of strain C3T was observed at 15–30 °C (optimum 25 °C), pH 6.0–9.0 (optimum pH 7.5), and in the presence of 1–7 % (w/v) NaCl (optimum 2–3 %). Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain C3T formed a distinct lineage within the family Flavobacteriaceae and exhibited the highest similarity (95.21 %) to the type strains of Maribacter dokdonensis, Maribacter arcticus, Maribacter orientalis and Maribacter stanieri, and ‘Maribacter caenipelagi’ HD-44. The only isoprenoid quinone present within strain C3T was menaquinone 6 (MK-6). The G+C content of genomic DNA was 41.5 mol%. The major polar lipids were phosphatidylethanolamine and three unidentified lipids. The predominant cellular fatty acids (>5 % of the total fatty acids) were iso-C15 : 1 G, iso-C15 : 0, iso-C15 : 0 3-OH, iso-C17 : 0 3-OH, and summed feature 3 (comprising C16 : 1ω7c and/or C16 : 1ω6c). On the basis of the phenotypic, chemotaxonomic and phylogenetic characteristics, strain C3T represents a novel species of the genus Maribacter, for which the name Maribacter flavus sp. nov. is proposed. The type strain is C3T ( = KCTC 42508T = CGMCC 1.15112T).