Kelp forest food webs as hot spots for the accumulation of microplastic and polybrominated diphenyl ether pollutants.

Kelp forests (KFs) are one of the most significant marine ecosystems in the planet. They serve as a refuge for a wide variety of marine species of ecological and economic importance. Additionally, they aid with carbon sequestration, safeguard the coastline, and maintain water quality. Microplastic (MP) and polybrominated diphenyl ethers (PBDEs) concentrations were analyzed across trophic levels in KFs around Todos Santos Bay. Spatial variation patterns were compared at three sites in 2021 and temporal change at Todos Santos Island (TSI) in 2021 and 2022. We analyzed these MPs and PBDEs in water, primary producers (Macrocystis pyrifera), grazers (Strongylocentrotus purpuratus), predators (Semicossyphus pulcher), and kelp detritus. MPs were identified in all samples (11 synthetic and 1 semisynthetic polymer) and confirmed using Fourier-transform infrared microspectroscopy-attenuated total reflectance (µ-FTIR-ATR). The most abundant type of MP is polyester fibers. Statistically significant variations in MP concentration were found only in kelps, with the greatest average concentrations in medium-depth kelps from TSI in 2022 (0.73 ± 0.58 MP g-1 ww) and in the kelp detritus from TSI in 2021 (0.96 ± 0.64 MP g-1 ww). Similarly, PBDEs were found in all samples, with the largest concentration found in sea urchins from Punta San Miguel (0.93 ± 0.24 ng g-1 ww). The similarity of the polymers can indicate a trophic transfer of MPs. This study shows the extensive presence of MP and PBDE subtropical trophic web of a KF, but correlating these compounds in environmental samples is highly complex, influenced by numerous factors that could affect their presence and behavior. However, this suggests that there is a potential risk to the systems and the services that KFs offer.

Chlorella sorokiniana UTEX 2805, a heat and intense, sunlight-tolerant microalga with potential for removing ammonium from wastewater.

In the summer of 2003, a microalga strain was isolated from a massive green microalgae bloom in wastewater stabilization ponds at the treatment facility of La Paz, B.C.S., Mexico. Prevailing environmental conditions were air temperatures over 40 degrees C, water temperature of 37 degrees C, and insolation of up to 2400 micromol m2 s(-1) at midday for several hours at the water surface for four months. The microalga was identified as Chlorella sorokiniana Shih. et Krauss, based on sequencing its entire 18S rRNA gene. In a controlled photo-bioreactor, this strain can grow to high population densities in synthetic wastewater at temperatures of 40-42 degrees C and light intensity of 2500 micromol m2 s(-1) for 5h daily and efficiently remove ammonium from the wastewater under these conditions better than under normal lower temperature (28 degrees C) and lower light intensity (60 micromol m2 s(-1)). When co-immobilized with the bacterium Azospirillum brasilense that promotes growth of microalgae, the population of microalga grew faster and removed even more ammonium. Under exposure to extreme growth conditions, the quantity of four photosynthetic pigments increased in the co-immobilized cultures. This strain of microalga has potential as a wastewater treatment agent under extreme conditions of temperature and light intensity.

GacA regulates the PTSNtr-dependent control of cyst formation in Azotobacter vinelandii.

Azotobacter vinelandii forms cysts resistant to desiccation and produces polyhydroxybutyrate (PHB), alginate and alkylresorcinols (ARs) that are components of mature cysts. The expression of genes involved in the synthesis of these compounds is under the control of the GacA-RsmA global regulatory system where the RsmA protein represses the translation of mRNAs involved in the synthesis of these polymers. The synthesis of PHB and ARs is also controlled by the Nitrogen-regulated phosphotransferase system (PTSNtr) global regulatory system. When unphosphorylated, the Enzyme IIANtr (EIIANtr) protein impairs the synthesis of PHB and ARs. Here we show that cells of gacA mutants, as well as mutants that carry the EIIANtr protein in its unphosphorylated state, have similar encysting negative phenotypes. Interestingly, we found that in the gacA mutant strain, the EIIANtr protein was present in its unphosphorylated state. These data indicated that in addition to the GacA-RsmA system, GacA controls polymer synthesis and encystment by controlling the phosphorylation of the EIIANtr, revealing a previously unrecognized link between GacA and PTSNtr.