Comparative membrane proteomics reveal contrasting adaptation strategies for coastal and oceanic marine Synechococcus cyanobacteria.

Marine cyanobacteria genus Synechococcus are among the most abundant and widespread primary producers in the open ocean. Synechococcus strains belonging to different clades have adapted distinct strategies for growth and survival across a range of marine conditions. Clades I and IV are prevalent in colder, mesotrophic, coastal waters, while clades II and III prefer warm, oligotrophic open oceans. To gain insight into the cellular resources these unicellular organisms invest in adaptation strategies we performed shotgun membrane proteomics of four Synechococcus spp. strains namely CC9311 (clade I), CC9605 (clade II), WH8102 (clade III) and CC9902 (clade IV). Comparative membrane proteomes analysis demonstrated that CC9902 and WH8102 showed high resource allocation for phosphate uptake, accounting for 44% and 38% of overall transporter protein expression of the species. WH8102 showed high expression of the iron uptake ATP-binding cassette binding protein FutA, suggesting that a high binding affinity for iron is possibly a key adaptation strategy for some strains in oligotrophic ocean environments. One protein annotated as a phosphatase 2c (Sync_2505 and Syncc9902_0387) was highly expressed in the coastal mesotrophic strains CC9311 and CC9902, constituting 14%-16% of total membrane protein, indicating a vital, but undefined function, for strains living in temperate mesotrophic environments.

Paleoproteomic evidence reveals dairying supported prehistoric occupation of the highland Tibetan Plateau.

The extreme environments of the Tibetan Plateau offer considerable challenges to human survival, demanding novel adaptations. While the role of biological and agricultural adaptations in enabling early human colonization of the plateau has been widely discussed, the contribution of pastoralism is less well understood, especially the dairy pastoralism that has historically been central to Tibetan diets. Here, we analyze ancient proteins from the dental calculus (n = 40) of all human individuals with sufficient calculus preservation from the interior plateau. Our paleoproteomic results demonstrate that dairy pastoralism began on the highland plateau by ~3500 years ago. Patterns of milk protein recovery point to the importance of dairy for individuals who lived in agriculturally poor regions above 3700 m above sea level. Our study suggests that dairy was a critical cultural adaptation that supported expansion of early pastoralists into the region's vast, non-arable highlands, opening the Tibetan Plateau up to widespread, permanent human occupation.