Investigating the Relationship Between Zetaproteobacteria and Cyanobacteria and its Implications for the Geological Record

Abstract

Banded Iron Formations (BIFs) are geological relics of the ancient oceans that were partially formed by microorganisms. This includes oxygenic phototrophs and iron-oxidizing bacteria (FeOB) whose relative contributions are likely influenced by their interactions with each other. Based on co-occurrence in modern environments, I propose that oxygenic phototrophs and microaerophilic FeOB may have a syntrophic relationship that aided their ability to contribute to BIF genesis. Ancient Cyanobacteria could have produced oxygen that oxidized iron while simultaneously stimulating the growth of marine microaerophilic iron-oxidizers, such as Zetaproteobacteria, by providing them oxygen in the largely anoxic ancient oceans. I first aim to identify evidence of this syntrophy within Zetaproteobacteria genomes. I constructed profile Hidden Markov Models for oxygen tolerance proteins to determine their presence in Zetaproteobacteria genomes and compared Zetaproteobacteria genomes from hydrothermal vent ecosystems to those from environments more likely to harbor Cyanobacteria. From these comparisons, we found little genomic evidence of a long term syntrophy, suggesting that their relationship may be opportunistic rather than tightly coupled. Currently a Cyanobacteria is being isolated from the same environment that the Zetaproteobacterium Mariprofundus erugo was cultivated. Microscopy suggests that a Synechococcus sp. and other coccoid Cyanobacteria are present in those phototrophic enrichment cultures. This isolate can be used in future co-culture experiments to further investigate this relationship and its implications for BIFs.