Editorial for the Special Issue: Advances in the Biology of Phototrophic Bacteria

Phototrophic bacteria represent a very ancient phylogenetic and highly diverse metabolic type of bacteria that diverged early into several major phylogenetic lineages with quite different properties. [...]

Assessment of Trametes versicolor, Isochrysis galbana, and Purple Phototrophic Bacteria for the Removal of Pharmaceutical Compounds in Hospital Wastewater

Hospitals are one of the key contributors of pharmaceutical contaminants of emerging concern to the sewer systems. Hospitals wastewaters contain concentrations of pharmaceutical compounds between 3 and 150, which are higher than urban wastewater streams. However, dedicated treatments of the hospital effluents before discharge to the sewer system are not compulsory. Besides, conventional wastewater treatment plants have not been designed to remove pharmaceutical compounds effectively, and consequently, these micropollutants can reach the aquatic ecosystems. The removal of pharmaceutical compounds in real hospital wastewater was gaged using three different microbial cultures (white rot-fungus Trametes versicolor, microalga Isochrysis galbana, and a mixed culture of non-sulfur purple phototrophic bacteria). Before and after bioassays of the hospital wastewater, environmental hazard quotients were used to evaluate the biological treatment efficiency. Up to 45 out of the 79 compounds included in the analytical method were noticed in the hospital wastewater, with a predominance of analgesics/anti-inflammatories (acetaminophen, ibuprofen, ketoprofen, and naproxen). It was followed by antibiotics (azithromycin, ciprofloxacin, and ofloxacin, out of which the first two are included in the watch list of substances for monitoring in water in 2020) and anti-hypertensive drugs. Isochrysis galbana reached a reduction of 45% of the total concentration of pharmaceuticals, whereas Trametes versicolor and mixed culture of purple phototrophic bacteria improved the reductions up to 69% and 76%, respectively. Moreover, potential environmental risk compounds (antibiotics, particularly ciprofloxacin and ofloxacin) were removed by Trametes versicolor in higher extension, obtaining a total hazard quotient reduction higher than the other two cultures. Removal efficiency and environmental risk assessment of remaining PhACs were used to evaluate the performance of the new biological systems for the treatment of emerging pollutants. According to both criteria, T. versicolor seems the most capable alternative for removing pharmaceutical compounds in hospital wastewater effluents.

Gullies and Moraines Are Islands of Biodiversity in an Arid, Mountain Landscape, Asgard Range, Antarctica

Cold, dry, and nutrient-poor, the McMurdo Dry Valleys of Antarctica are among the most extreme terrestrial environments on Earth. Numerous studies have described microbial communities of low elevation soils and streams below glaciers, while less is known about microbial communities in higher elevation soils above glaciers. We characterized microbial life in four landscape features (habitats) of a mountain in Taylor Valley. These habitats varied significantly in soil moisture and include moist soils of a (1) lateral glacial moraine, (2) gully that terminates at the moraine, and very dry soils on (3) a southeastern slope and (4) dry sites near the gully. Using rRNA gene PCR amplicon sequencing of Bacteria and Archaea (16S SSU) and eukaryotes (18S SSU), we found that all habitat types harbored significantly different bacterial and eukaryotic communities and that these differences were most apparent when comparing habitats that had macroscopically visible soil crusts (gully and moraine) to habitats with no visible crusts (near gully and slope). These differences were driven by a relative predominance of Actinobacteria and a Colpodella sp. in non-crust habitats, and by phototrophic bacteria and eukaryotes (e.g., a moss) and predators (e.g., tardigrades) in habitats with biological soil crusts (gully and moraine). The gully and moraine also had significantly higher 16S and 18S ESV richness than the other two habitat types. We further found that many of the phototrophic bacteria and eukaryotes of the gully and moraine share high sequence identity with phototrophs from moist and wet areas elsewhere in the Dry Valleys and other cold desert ecosystems. These include a Moss (Bryum sp.), several algae (e.g., a Chlorococcum sp.) and cyanobacteria (e.g., Nostoc and Phormidium spp.). Overall, the results reported here broaden the diversity of habitat types that have been studied in the Dry Valleys of Antarctica and suggest future avenues of research to more definitively understand the biogeography and factors controlling microbial diversity in this unique ecosystem.