Nitrogen Fixation Activity and Genome Analysis of a Moderately Haloalkaliphilic Anoxygenic Phototrophic Bacterium Rhodovulum tesquicola.

The genome of the moderately haloalkaliphilic diazotrophic anoxygenic phototrophic bacterium Rhodovulum tesquicola A-36sT isolated from an alkaline lake was analyzed and compared to the genomes of the closest species Rhodovulum steppense A-20sT and Rhodovulum strictum DSM 11289T. The genomic features of three organisms are quite similar, reflecting their ecological and physiological role of facultative photoheterotrophs. Nevertheless, the nitrogenase activity of the pure cultures of the studied bacteria differed significantly: the highest rate (4066 nmoles C2H2/mg of dry weight per hour) was demonstrated by Rhodovulum strictum while the rates in Rhodovulum tesquicola and Rhodovulum steppense were an order of magnitude lower (278 and 523 nmoles C2H2/mg of dry weight per hour, respectively). This difference can be attributed to the presence of an additional nitrogenase operon found exclusively in R. strictum and to the structural variation in nitrogenase operon in R. tesquicola.

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2)-Specific T Cells and Antibodies in Coronavirus Disease 2019 (COVID-19) Protection: A Prospective Study.

BACKGROUND: During the ongoing coronavirus disease 2019 (COVID-19) pandemic, many individuals were infected with and have cleared the virus, developing virus-specific antibodies and effector/memory T cells. An important unanswered question is what levels of T-cell and antibody responses are sufficient to protect from the infection. METHODS: In 5340 Moscow residents, we evaluated anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) immunoglobulin M (IgM)/immunoglobulin G (IgG) titers and frequencies of the T cells specific to the membrane, nucleocapsid, and spike proteins of SARS-CoV-2, using interferon gamma (IFN-γ) enzyme-linked immunosorbent spot (ELISpot) assay. Additionally, we evaluated the fractions of virus-specific CD4+ and CD8+ T cells using intracellular staining of IFN-γ and interleukin 2 followed by flow cytometry. We analyzed the COVID-19 rates as a function of the assessed antibody and T-cell responses, using the Kaplan-Meier estimator method, for up to 300 days postinclusion. RESULTS: We showed that T-cell and antibody responses are closely interconnected and are commonly induced concurrently. Magnitudes of both responses inversely correlated with infection probability. Individuals positive for both responses demonstrated the highest levels of protectivity against the SARS-CoV-2 infection. A comparable level of protection was found in individuals with antibody response only, whereas the T-cell response by itself granted only intermediate protection. CONCLUSIONS: We found that the contribution of the virus-specific antibodies to protection against SARS-CoV-2 infection is more pronounced than that of the T cells. The data on the virus-specific IgG titers may be instructive for making decisions in personalized healthcare and public anti-COVID-19 policies. Clinical Trials Registration. NCT04898140.

AlgalTextile - a new biohybrid material for wastewater treatment.

Efficient nutrient extraction from wastewater and reuse as bio-fertilizer is an important task for reducing anthropogenic load toward circular economy. Inspired by microbial mats and biofilms, we developed a new material AlgalTextile (AT) that effectively absorbs nutrients from a medium. AT consists of three fully organic components: microalgae, alginate and textile. AT sequestered up to 99% of phosphorus (P-PO4) and 76% of total bound nitrogen from a medium. The uptake rate of phosphorus and nitrogen by AT was highest among all methods using photosynthetic microorganisms, but lower than EBPR and physicochemical methods for phosphorus removal, and anammox and denitrifying bacteria for nitrogen removal. Advantages of AT are its easy production, possibility of seasonal use and utilization as fertilizer. AT as biofertilizer for cress resulted in 35% greater length compared to the control. This outlines a promising technique for seasonal wastewater treatment, improving soil fertility and treatment of polluted surface runoff.

Draft Genome Sequence of "Halomonas chromatireducens" Strain AGD 8-3, a Haloalkaliphilic Chromate- and Selenite-Reducing Gammaproteobacterium.

Here, we report the complete genome sequence (3.97 Mb) of "Halomonas chromatireducens" AGD 8-3, a denitrifying bacterium capable of chromate and selenite reduction under extreme haloalkaline conditions. This strain was isolated from soda solonchak soils of the Kulunda steppe, Russian Federation.

Rhodovulum tesquicola sp. nov., a haloalkaliphilic purple non-sulfur bacterium from brackish steppe soda lakes.

Two strains of purple non-sulfur bacteria (A-36s(T) and A-51s) were isolated from brackish steppe soda lakes of southern Siberia. Genetically, the isolates were related most closely to the type strains of Rhodovulum steppense and Rhodovulum strictum, from which they differed at the species level (98.5% 16S rRNA gene sequence similarity, 40-53% DNA-DNA relatedness). Cells of the two strains were ovoid to rod-shaped, 0.4-0.8 µm wide and 1.0-2.5 µm long, and motile by means of a polar flagellum. They contained internal photosynthetic membranes of vesicular type and photosynthetic pigments (bacteriochlorophyll a and carotenoids of the spheroidene series). The strains were obligate haloalkaliphiles, growing over wide ranges of salinity (0.3-10.0% NaCl) and pH (7.5-10.0), with growth optima at 1.0-3.0% NaCl and pH 8.5-9.0. Photoheterotrophic and chemoheterotrophic growth occurred with a number of organic compounds and biotin, p-aminobenzoate, thiamine and niacin as growth factors. No anaerobic respiration on nitrite, nitrate or fumarate and no fermentation were demonstrated. The strains grew photolithoautotrophically and chemolithoautotrophically with sulfide, sulfur and thiosulfate, oxidizing them to sulfate. Sulfide was oxidized via deposition of extracellular elemental sulfur. No growth with H(2) as the electron donor was observed. The major fatty acid was C(18:1) (78%). The major quinone was ubiquinone Q-10. The DNA G+C content of strain A-36s(T) was 65.4 mol% (T(m)). According to genotypic and phenotypic characteristics, the investigated strains were assigned to a novel species of the genus Rhodovulum, for which the name Rhodovulum tesquicola sp. nov. is proposed. The type strain is A-36s(T) ( = VKM B-2491(T) = ATCC BAA-1573(T)), which was isolated from steppe soda lake Sul'fatnoe (Zabaikal'skii Krai, southern Siberia, Russia).

Rhodovulum steppense sp. nov., an obligately haloalkaliphilic purple nonsulfur bacterium widespread in saline soda lakes of Central Asia.

Seven strains of purple nonsulfur bacteria isolated from the shallow-water steppe soda lakes of the cryoarid zone of Central Asia formed a genetically homogeneous group within the genus Rhodovulum. The isolates were most closely related to Rhodovulum strictum, from which they differed at the species level (99.5 % 16S rRNA gene identity and 42-44 % DNA-DNA hybridization level). According to genotypic and phenotypic characteristics, the strains were assigned to a new species of the genus Rhodovulum, for which the name Rhodovulum steppense sp. nov. is proposed. Cells of all strains were ovoid to rod-shaped, 0.3-0.8 microm wide and 1-2.5 microm long, and motile by means of polar flagella. They contained internal photosynthetic membranes of the vesicular type and photosynthetic pigments (bacteriochlorophyll a and carotenoids of the spheroidene series). All strains were obligate haloalkaliphiles, growing within a wide range of salinity (0.3-10 %) and pH (7.5-10), with growth optima at 1-5 % NaCl and pH 8.5. Photo- and chemoheterotrophic growth occurred with a number of organic compounds and biotin, thiamine and niacin as growth factors. No anaerobic respiration on nitrite, nitrate or fumarate and no fermentation was demonstrated. Bacteria grew photo- and chemolithoautotrophically with sulfide, sulfur and thiosulfate, oxidizing them to sulfate. Sulfide was oxidized via deposition of extracellular elemental sulfur. No growth with H(2) as electron donor was demonstrated. The major fatty acid was 18 : 1 (81.0 %). The major quinone was Q-10. The DNA G+C content was 66.1 mol% (T(m)). The type strain, A-20s(T) (=VKM B-2489(T) =DSM 21153(T)), was isolated from soda lake Khilganta (Zabaikal'skii Krai, southern Siberia, Russia).