Transcriptomic analyses unravel differential expression of genes involved in the N-glycosylation pathway of Phaeodactylum tricornutum ecotypes

Most of the biologics are glycoproteins. It is well-established that N-glycans harboured by proteins are involved in the protein half-life, bioactivity and immunogenicity. Currently, most of the biologics are produced in mammalian cells. However, microalgae emerged as a cheaper alternative biofactory. Among them, the diatom Phaeodactylum tricornutum benefits from numerous advantages and has been successfully used to produce biologics such as SARS-COV2 RBD and functional monoclonal antibodies (mAbs). These mAbs have been demonstrated to be glycosylated with oligomannosides that are similar to the mammalian ones and that result from processing steps occurring in the ER and the early Golgi apparatus. Surprisingly, these oligomannosides represent the major N-glycans population even if the diatom possesses glycoenzymes potentially involved in the biosynthesis of complex-type N-glycans in the Golgi apparatus. Therefore, it is essential to characterize the regulation of the P. tricornutum protein N-glycosylation pathway as well as the expression level of genes involved in the N-glycosylation of proteins. In the present work, we performed RNA-Seq analyses on different ecotypes of P. tricornutum and decode the differential expression of genes involved in the protein N-glycosylation pathway.

Products released from surgical face masks can provoke cytotoxicity in the marine diatom Phaeodactylum tricornutum.

Surgical face masks are more present than ever as personal protective equipment due to the COVID-19 pandemic. In this work, we show that the contents of regular surgical masks: i) polypropylene microfibres and ii) some added metals such as: Al, Fe, Cu, Mn, Zn and Ba, may be toxic to some marine life. This work has got two objectives: i) to study the release rate of the products from face masks in marine water and ii) to assess the toxicity in Phaeodactylum tricornutum of these by-products. To achieve these two objectives, we performed release kinetic experiments by adding masks in different stages of fragmentation to marine water (i.e. whole face masks and fragments of them 1.52 ± 0.86 mm). Released microfibres were found after one month in shaking marine water; 0.33 ± 0.24 and 21.13 ± 13.19 fibres·mL-1 were collected from the whole and fragmented face masks, respectively. Significant amounts of dissolved metals such as Mn, Zn and Ni, as well as functional groups only in the water containing the face mask fragments were detected. Water from both treatments was employed to study its toxicity on the marine diatom. Only the water from the face mask fragments showed a significant, dose-dependent, decrease in cell density in P. tricornutum; 53.09 % lower than in the controls. Although the water from the face mask fragments showed greater effects on the microalgae population than the water from the whole face mask, the latter treatment did show significant changes in the photosynthetic apparatus and intrinsic properties of the cells. These results indicate that during fragmentation and degradation face masks a significant chemical print can be observed in the marine environment.