Trypsin is best known as a digestive enzyme in animals, but remains unexplored in phytoplankton, the major primary producers in the ocean. Here we report the prevalence of trypsin genes in global ocean phytoplankton and significant influences of environmental nitrogen (N) and phosphorus (P) on their expression. Using CRISPR/Cas9 mediated-knockout and overexpression analyses, we further reveal that a trypsin in Phaeodactylum tricornutum (PtTryp2) functions to repress N acquisition, but its expression decreases under N-deficiency to promote N acquisition. On the contrary, PtTryp2 promotes phosphate uptake per se, and its expression increases under P-deficiency to further reinforce P acquisition. Furthermore, PtTryp2 knockout led to amplitude magnification of the nitrate and phosphate uptake ‘seesaw’, whereas PtTryp2 overexpression dampened it, linking PtTryp2 to stabilizing N:P stoichiometry. Our data demonstrate that PtTryp2 is a coordinate regulator of N:P stoichiometric homeostasis. The study opens a window for deciphering how phytoplankton adapt to nutrient-variable marine environments.
A Gram-stain-negative, non-motile, ovoid or short rod shaped and aerobic marine bacterium, designated as strain LXJ103T, was isolated from a coastal phytoplankton bloom in Xiamen, PR China. Cells were oxidase- and catalase-positive. Strain LXJ103T grew at 4–40 °C (optimum, 28–37 °C), at pH 6–10 (optimum, pH 8.5) and with 1–15 % (w/v) NaCl (optimum, 3 %). The major cellular fatty acids (>10 %) were iso-C18 : 1 ω7c/iso-C18 : 1 ω6c (70.2 %) and C16 : 0 (10.3 %). The following polar lipids were found to be present: phosphatidylglycerol, phosphatidylethanolamine, two unidentified phospholipids and five unknown glycolipids. The predominant respiratory quinone was ubiquinone-10. Strain LXJ103T exhibited the highest 16S rRNA gene sequence similarity to Roseovarius litorisediminis D1-W8T (96.97 %). The phylogenetic trees based on 16S rRNA gene sequences showed that strain LXJ103T was a member of the genus Roseovarius . The draft genome size of strain LXJ103T is 3.05 Mb with a genomic G+C content of 61.22 mol%. The digital DNA–DNA genome hybridization value of strain LXJ103T compared with the most similar type strain R. litorisediminis CECT 8287T was 18.80 %. The average nucleotide identity value between strain LXJ103T and R. litorisediminis CECT 8287T was 72.60 %. On the basis of polyphasic data, strain LXJ103T represents a novel species of the genus Roseovarius , for which the name Roseovarius carneus sp. nov. is proposed. The type strain is LXJ103T (=CGMCC 1.19168T=MCCC 1K06527T=JCM 34778T).
Trypsin is an ancient protease best known as a digestive enzyme in animals, and traditionally believed to be absent in plants and protists. Here, we surveyed the distribution, diversity, evolution and potential functions of trypsin genes in global ocean phytoplankton, the major primary producers in the aquatic ecosystem. Our analysis indicates that trypsin genes are widely distributed both taxonomically and geographically in marine phytoplankton. Furthermore, by systematic comparative analyses we documented lineage-specific diversity and expansion of trypsin genes in the evolution of marine phytoplankton. Genome-wide analyses revealed that trypsin genes were more prevalent in diatoms than in other lineages. Moreover, the expression of trypsin genes in diatom tended to be more responsive to environmental stimuli. The duplication and neofunctionalization of trypsin genes may be important in diatoms to adapt to dynamical environmental conditions, contributing to diatoms’ dominance in the coastal oceans. This work advances our knowledge on the distributions and neofunctionalizations of this ancient enzyme and creates a new research direction in the phytoplankton biology.
A novel Gram-stain-negative, non-flagellated, non-motile, rod-shaped (0.4–0.6×1.8–2.5 µm), aerobic bacterial strain, designated JLT21T, was isolated from seawater of a shallow-sea hydrothermal system. Growth occurred with 0–4.0 % (w/v) NaCl (optimum, 2.0 % NaCl), at 8–45 °C (optimum, 25 °C) and at pH 3.0–10.0 (optimum, pH 7.0). Analysis of 16S rRNA gene sequences revealed that strain JLT21T showed the highest 16S rRNA gene sequence similarity to Gaetbulibacter aquiaggeris KEM-8T (97.2 %), Gaetbulibacter marinus IMCC1914T (96.9 %) and Yeosuana aromativorans GW1-1T (96.9 %). Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain JLT21T clustered with Y. aromativorans GW1-1T. The predominant respiratory quinone of strain JLT21T was menaquinone-6 (MK-6). Polar lipids were phosphatidylcholine, phosphatidylglycerol, phosphatidylethanolamine, three unidentified glycolipids and four unidentified lipids. The major fatty acids of strain JLT21T were iso-C15 : 0 (21.7 %), C16 : 1 ω6c/ω7c (11.5 %) and iso-C17 : 0 3-OH (10.9 %). The DNA G+C content of strain JLT21T was 32.6 %. On the basis of polyphasic analysis, strain JLT21T is considered to represent a novel species of the genus Yeosuana , for which the name Yeosuana marina sp. nov. is proposed. The type strain of Yeosuana marina is JLT21T (=CGMCC 1.15787T=JCM 31511T). The study helps us better understand the bacterial species in the shallow-sea hydrothermal system and their adaptations to the hydrothermal environment.
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