A Comprehensive Study of Cyanobacterial Morphological and Ecological Evolutionary Dynamics through Deep Geologic Time

Abstract

Cyanobacteria have exerted a profound influence on the progressive oxygenation of Earth. As a complementary approach to examining the geologic record—phylogenomic and trait evolutionary analyses of extant species can lead to new insights. We constructed new phylogenomic trees and analyzed phenotypic trait data using novel phylogenetic comparative methods. We elucidated the dynamics of trait evolution in Cyanobacteria over billion-year timescales, and provide evidence that major geologic events in early Earth’s history have shaped—and been shaped by—evolution in Cyanobacteria. We identify a robust core cyanobacterial phylogeny and a smaller set of taxa that exhibit long-branch attraction artifacts. We estimated the age of nodes and reconstruct the ancestral character states of 43 phenotypic characters. We find high levels of phylogenetic signal for nearly all traits, indicating the phylogeny carries substantial predictive power. The earliest cyanobacterial lineages likely lived in freshwater habitats, had small cell diameters, were benthic or sessile, and possibly epilithic/endolithic with a sheath. We jointly analyzed a subset of 25 binary traits to determine whether rates of trait evolution have shifted over time in conjunction with major geologic events. Phylogenetic comparative analysis reveal an overriding signal of decreasing rates of trait evolution through time. Furthermore, the data suggest two major rate shifts in trait evolution associated with bursts of evolutionary innovation. The first rate shift occurs in the aftermath of the Great Oxidation Event and “Snowball Earth” glaciations and is associated with decrease in the evolutionary rates around 1.8–1.6 Ga. This rate shift seems to indicate the end of a major diversification of cyanobacterial phenotypes–particularly related to traits associated with filamentous morphology, heterocysts and motility in freshwater ecosystems. Another burst appears around the time of the Neoproterozoic Oxidation Event in the Neoproterozoic, and is associated with the acquisition of traits involved in planktonic growth in marine habitats. Our results demonstrate how uniting genomic and phenotypic datasets in extant bacterial species can shed light on billion-year old events in Earth’s history.

Morphological and isotopic changes of heterocystous cyanobacteria in response to N2 partial pressure

“…Fossilized cyanobacteria with convincing heterocysts have been found in the 400-million-year (Ma)-old Rhynie Chert of Scotland (Croft & George, 1959), but most reports of older fossil heterocysts (e.g., Figure 6; Schopf, 1968;Licari & Cloud, 1968Cloud, 1976;Awramik & Barghoorn, 1977;Nagy, 1978) are disputed, so cannot reliably be used for interpreting ancient pN 2 . Time calibrations based on integrated phylogenetic and phenotypic data suggest that heterocystous cyanobacteria evolved 2,450-2,100 Ma ago (Tomitani et al, 2006), but possibly more recently (Uyeda, Harmon, & Blank, 2016). Alternatively, heterocystous cyanobacteria may have evolved well after other cyanobacterial assemblages, as has been proposed following phylogenetic analyses of single 1990), although oxygenic "whiffs" may have appeared in the Archean (Anbar et al, 2007).…”

“…Most importantly, more δ 15 N measurements from Precambrian rocks are needed, yet the geologic record of early Earth is not well preserved due to metamorphic and diagenetic overprints that obscure δ 15 N signals . However, given that heterocystous cyanobacteria likely evolved well after the early Archean (Tomitani et al, 2006;Uyeda et al, 2016), information on the pN 2 -dependent isotopic response of nonheterocystous diazotrophs is needed to more reliably interrogate δ 15 N from early Earth through this approach. Biological nitrogen preserved from the early Archean may satisfy such conditions, as nitrogen fixation dominated while denitrification was virtually nonexistent during this time (Stüeken et al, 2015;Thomazo & Papineau, 2013).…”

Key questions and challenges in angiosperm macroevolution

“…We need to systematically test and account for heterogeneity in macroevolutionary rates and processes through time and among lineages Heterogeneity is increasingly recognized as a key challenge in macroevolution (O'Meara, 2012), affecting molecular, morphological, diversification and fossilization rates, especially at large taxonomic scales and over long geological periods (Figs 2, 3). Current methods typically only allow for one form of heterogeneity, for example either lineage-specific rate/process shifts (O'Meara et al, 2006;Alfaro et al, 2009;Venditti et al, 2011;Rabosky, 2014) or global, epoch-specific rates/processes (Stadler, 2011;May et al, 2015;Uyeda et al, 2016). Future methods should attempt to model both among-lineage and through-time heterogeneity in a unified framework.…”

Human Anticancers and Antidiabetic Activities of the Cyanobacterium Fischerella sp. BS1-EG Isolated from River Nile, Egypt

“…Hormogonia composed from small cylindrical cells which enlarge and become rounded (Fig 1.). Concerning the ecological distribution of Fischerella, it is reported that it is mostly found in both terrestrial and aquatic environments (Uyeda et al, 2016) In addition, the chemical composition of Fischerella BS1-EG extract was determined using trace GC Ultra-ICQ mass spectrometer (Fig.2). Also results in Table (3), showed that 29 different compounds were detected and identified as fatty acids, alkaloides, phenols and amino acids.…”