Convergent photophysiology and prokaryotic assemblage structure in epilithic cyanobacterial tufts and algal turf communities.

As global change spurs shifts in benthic community composition on coral reefs globally, a better understanding of the defining taxonomic and functional features that differentiate proliferating benthic taxa is needed to predict functional trajectories of reef degradation better. This is especially critical for algal groups, which feature dramatically on changing reefs. Limited attention has been given to characterizing the features that differentiate tufting epilithic cyanobacterial communities from ubiquitous turf algal assemblages. Here, we integrated an in situ assessment of photosynthetic yield with metabarcoding and shotgun metagenomic sequencing to explore photophysiology and prokaryotic assemblage structure within epilithic tufting benthic cyanobacterial communities and epilithic algal turf communities. Significant differences were not detected in the average quantum yield. However, variability in yield was significantly higher in cyanobacterial tufts. Neither prokaryotic assemblage diversity nor structure significantly differed between these functional groups. The sampled cyanobacterial tufts, predominantly built by Okeania sp., were co-dominated by members of the Proteobacteria, Firmicutes, and Bacteroidota, as were turf algal communities. Few detected ASVs were significantly differentially abundant between functional groups and consisted exclusively of taxa belonging to the phyla Proteobacteria and Firmicutes. Assessment of the distribution of recovered cyanobacterial amplicons demonstrated that alongside sample-specific cyanobacterial diversification, the dominant cyanobacterial members were conserved across tufting cyanobacterial and turf algal communities. Overall, these data suggest a convergence in taxonomic identity and mean photosynthetic potential between tufting epilithic cyanobacterial communities and algal turf communities, with numerous implications for consumer-resource dynamics on future reefs and trajectories of reef functional ecology.

Survival of an Antarctic cyanobacterial mat under Martian conditions.

Antarctica is one of the most outstanding analogs of Mars, and cyanobacterial mats are considered one of the most resilient biological consortia. The purpose of this study is to find out the effect of the Martian conditions on an Antarctic cyanobacterial mat. We exposed an Antarctic microbial mat to Martian conditions in a simulating chamber (MARTE) for 15 d and investigated the variations in the consortium by the use of 16S rRNA gene expression as an indicator of the biological activity. Metabarcoding using the V3-V4 regions of the 16S rRNA gene was used to determine the succession of the active members of the microbial consortium during the experiment. The results showed that the microbial mat, far from collapsing, can survive the stringent conditions in the simulating chamber. Different behaviors were displayed depending on the metabolic capabilities and physiological characteristics of every taxon. The main conclusion is that the Martian conditions did not impair growth in some of the groups, and thus, the investigated Antarctic community would be able to survive in a Martian environment at least during the short experimental period, although elements of the community were affected in different ways.

Cultivation of algal biofilm and mat communities from the Garhwal Himalayas for possible use in diverse biotechnological applications.

The current study aimed to screen biofilm-/mat-forming and fast-growing algal communities from the Garhwal Himalayas, India. A total of 15 biofilm/mat-forming algal samples were collected, 8 biofilms out of these could be cultured and analyzed for their growth and development with time. Light microscopy was used to identify different types of cyanobacteria and algae present in the different collected biofilms/mats. Four biofilm and mat communities, namely biofilms #E, #F, #G, and #H, were found to have fast growth and were quick to colonize the substratum. Nylon net was identified as the most cost-effective and best-supporting material for biofilm development and biomass production. The study also found that increasing the harvesting frequency from the nylon net-enmeshed biofilms at least once a week would enhance the final biomass yield compared to harvesting the community once after a longer growth duration. Nevertheless, the findings reported here will be useful for researchers in developing phototrophic biofilm-based technology using nylon net, as it will be mechanically strong, supportive, and easy to handle.

Efficiency of extremophilic microbial mats for removing Pb(II), Cu(II), and Ni(II) ions from aqueous solutions.

Two different extremophilic films were used as natural biosorbents to remove Cu(II), Ni(II), and Pb(II) from aqueous solutions. Surface area, scanning electron microscopy imaging, and Fourier transformation infrared spectroscopy were used to characterize the surfaces of the biosorbents. The results indicated high affinity of the biosorbents to remove Pb(II), Cu(II), and Ni(II), with adsorption rates ranging from 73.6 to 100% for both biosorbents. The biosorbents succeed in removing the metal ions from aqueous mixtures in the following order: Pb(II) > Cu(II) > Ni(II). The maximum removal rates of metal ions were achieved at pH 6, contact time of 150 min, biosorbent dose of 2.5 g/L, and metal ion concentration of 50 mg/L. The isothermal studies showed that both Langmuir and Freundlich models well expressed the adsorption process. Kinetically, the pseudo-second-order reaction better expressed the type of reaction than the pseudo-first-order reaction.

Cyanotoxin release from the benthic, mat-forming cyanobacterium Microseira (Lyngbya) wollei in the St. Lawrence River, Canada.

Benthic cyanobacterial mats occurring in the St. Lawrence River fluvial lakes Saint-Louis and Saint-Pierre are dominated by Microseira (Lyngbya) wollei which produce several cyanotoxins including LWTX-1 that is characteristic of Microseira wollei. This cyanotoxin is not only present in the filaments forming benthic mats, but was also measured in the water overlying the mats. LWTX-1 was found in all cyanobacterial filament samples (75.29-103.26 ng mg-1) and all overlying water samples (3.01-11.03 ng L-1). Toxin concentrations measured in overlying water and dry biomass were strongly correlated (r = 0.94). Furthermore, LWTX-1 concentration in water was positively correlated with the dissolved organic carbon in water (r = 0.74) and % nitrogen content in cyanobacterial filaments (r = 0.52). A preliminary study was conducted to determine the release and degradation rates of LWTX-1 from a M. wollei mat kept under laboratory conditions over a 3-month period. Toxin measurements revealed an early, massive toxin release followed by a typical decaying function, with a half-life in the order of 17 days. Our results raise concerns about the occurrence and downstream advection of dissolved cyanotoxins from Microseira mats in the aquatic environment. Graphical abstract.

Genome sequence of the moderately thermophilic sulfur-reducing bacterium Thermanaerovibrio velox type strain (Z-9701(T)) and emended description of the genus Thermanaerovibrio.

Thermanaerovibrio velox Zavarzina et al. 2000 is a member of the Synergistaceae, a family in the phylum Synergistetes that is already well-characterized at the genome level. Members of this phylum were described as Gram-negative staining anaerobic bacteria with a rod/vibrioid cell shape and possessing an atypical outer cell envelope. They inhabit a large variety of anaerobic environments including soil, oil wells, wastewater treatment plants and animal gastrointestinal tracts. They are also found to be linked to sites of human diseases such as cysts, abscesses, and areas of periodontal disease. The moderately thermophilic and organotrophic T. velox shares most of its morphologic and physiologic features with the closely related species, T. acidaminovorans. In addition to Su883(T), the type strain of T. acidaminovorans, stain Z-9701(T) is the second type strain in the genus Thermanaerovibrio to have its genome sequence published. Here we describe the features of this organism, together with the non-contiguous genome sequence and annotation. The 1,880,838 bp long chromosome (non-contiguous finished sequence) with its 1,751 protein-coding and 59 RNA genes is a part of the G enomic E ncyclopedia of Bacteria and Archaea project.