Nontoxic Strains of Cyanobacteria Are the Result of Major Gene Deletion Events Induced by a Transposable Element

Blooms that are formed by cyanobacteria consist of toxic and nontoxic strains. The mechanisms that result in the occurrence of nontoxic strains are enigmatic. All the nontoxic strains of the filamentous cyanobacterium Planktothrix that were isolated from 9 European countries were found to have lost 90% of a large microcystin synthetase (mcy) gene cluster that encoded the synthesis of the toxic peptide microcystin (MC). Those strains still contain the flanking regions of the mcy gene cluster along with remnants of the transposable elements that are found in between. The majority of the strains still contain a gene coding for a distinct thioesterase type II (mcyT), which is putatively involved in MC synthesis. The insertional inactivation of mcyT in an MC-producing strain resulted in the reduction of MC synthesis by 94 ± 2% (1 standard deviation). Nontoxic strains that occur in shallow lakes throughout Europe form a monophyletic lineage. A second lineage consists of strains that contain the mcy gene cluster but differ in their photosynthetic pigment composition, which is due to the occurrence of strains that contain phycocyanin or large amounts of phycoerythrin in addition to phycocyanin. Strains containing phycoerythrin typically occur in deep-stratified lakes. The rare occurrence of gene cluster deletion, paired with the evolutionary diversification of the lineages of strains that lost or still contain the mcy gene cluster, needs to be invoked in order to explain the absence or dominance of toxic cyanobacteria in various habitats

Factors associated with hospital admission and adverse outcome for COVID-19: Role of social factors and medical care

International audienceBackground: Beyond sex, age, and various comorbidities, geographical origin and socioeconomic deprivation are associated with Coronavirus Disease (COVID-19) morbidity and mortality in the general population. We aimed to assess factors associated with severe forms of COVID-19 after a hospital emergency department visit, focusing on socioeconomic factors. Methods: Patients with laboratory-confirmed COVID-19 attending the emergency department of Béclère Hospital (France) in March–April 2020 were included. Postal addresses were used to obtain two geographical deprivation indices at the neighborhood level. Factors associated with hospitalization and factors associated with adverse outcomes, i.e. mechanical ventilation or death, were studied using logistic and Cox analyses, respectively. Results: Among 399 included patients, 321 were hospitalized. Neither geographical origin nor socioeconomic deprivation was associated with any of the outcomes. Being male, older, overweight or obese, diabetic, or having a neuropsychiatric disorder were independent risk factors for hospitalization. Among 296 patients hospitalized at Béclère Hospital, 91 experienced an adverse outcome. Older age, being overweight or obese, desaturation and extent of chest CT scan lesions > 25% at admission (aHR: 2.2 [95% CI: 1.3–3.5]) and higher peak CRP levels and acute kidney failure (aHR: 2.0 [1.2–3.3]) during follow-up were independently associated with adverse outcomes, whereas treatment with hydrocortisone reduced the risk of mechanical ventilation or death by half (aHR: 0.5 [0.3–0.8]). Conclusion: No association between geographical origin or socioeconomic deprivation and the occurrence of a severe form of COVID-19 was observed in our population after arrival to the emergency department. Empirical corticosteroid use with hydrocortisone had a strong protective impact