Prochlorococcus and Synechococcus marine cyanobacteria: a scientometrics review

Abstract

The cyanobacteria Prochlorococcus and Synechococcus are the dominant primary producers in the ocean and perform a significant percentage of ocean carbono fixation. In the past, these cells were identified in flow cytometry, but nowadays, the genomic techniques bring different analyses that also identify clades and ecotypes; comparative genomics has helped to answer patterns of evolution and diversity among microbes. The genetic and genomic data increased the number of available Prochlorococcus genomes and facilitated evolutionary biology, microbial ecology, and biological oceanography. Therefore, this review summarizes the available data in the literature (1992–2021; n=480) using CiteSpace software to provide insights into the specific characteristics of Prochlorococcus and Synechococcus genes that scientists can use for establishing future research directions. From 1992 to 2021, the most frequent and with higher centrality keyword was "multiple evolutionary origin" (0.43), followed by flow cytometry (0.40), because this period was the main method used to identify cyanobacteria. In 2001-2010, the keywords with higher centrality were "sequence" and "gene", both with 0.13 of centrality; this can be explained by the period when gene sequencing was developed. In the last 10 years period 2011-2021 the keywords with higher centrality were diversity - 0.17; marine Synechococcus - 0.10; Prochlorococcus ecotype - 0.08; gene expression - 0.14; phytoplankton - 0.09; and light - 0.07. Additionally, the migration characteristics of flow cytometry, genes identification methods, genomes, ecotypes of cyanobacteria, and phytoplankton diversity indicate how future studies should focus.