Chemosensory response of marine flagellate towards L- and D- dissolved free amino acids generated during heavy grazing on bacteria

This study investigated the generation of dissolved free amino acids (DFAA) by the bacterivorous flagellate Rhynchomonas nasuta when feeding on abundant prey. Specifically, it examined whether this flagellate protist exhibits a chemosensory response towards those amino acids. The concentrations of glycine and the and D-enantiomers of glutamate, serine, threonine, alanine, and leucine were determined in co-cultures of the flagellate and bacteria. Glycine, L- and D-alanine, and L-serine were found to accumulate under these conditions in amounts that correlated positively with flagellate abundance, suggesting that protists are involved in their generation. Investigations of the chemotactic response of young and old foraging protists to the same amino acids, offered in concentrations similar to those previously generated, showed that glycine elicited the strongest attraction in both age groups. Young protists were strongly attracted to all the assayed amino acids, whereas older protists maintained a high level of attraction only for glycine. These results suggest that glycine generated by protists actively grazing in bacterially enriched patches functions as an infochemical, signaling to foraging protists the presence of available prey in the aquatic environment.

El efecto de la acidificación de los océanos sobre microalgas de la división chlorophyta

Se cultivaron tres cepas de la división Chlorophyta (Nephroselmis pyriformis cepa CGA7, Pyramimonas orientalis cepa CGA13 y Pyramimonas propulsa cepa CGA16) en medios a cuatro pH diferentes (rango desde un control a pH 8.1 a pH7.2). Se midieron las tasas de crecimiento para cada cepa y tratamiento. Las cepas no mostraron una respuesta uniforme a la acidificación del medio, aunque todas mostraron un incremento de sus tasas de crecimiento a pH 7.5. Únicamente N. pyriformis mostró un incremento de sus tasas de crecimiento a pH 7.2. Se concluye que la división Chlorophyta no muestra una respuesta uniforme a la acidificación del medio, pero que las tasas de crecimiento pueden verse incrementadas para las especies testadas en futuros escenarios de acidificación de los océanos.