The Complex Transcriptional Response of Acaryochloris marina to Different Oxygen Levels

Abstract

Ancient oxygenic photosynthetic prokaryotes produced oxygen as a waste product, but existed for a long time under an oxygen-free (anoxic) atmosphere, before an oxic atmosphere emerged. The change in oxygen levels in the atmosphere influenced the chemistry and structure of many enzymes that contained prosthetic groups that were inactivated by oxygen. In the genome of Acaryochloris marina, multiple gene copies exist for proteins that are normally encoded by a single gene copy in other cyanobacteria. Using high throughput RNA sequencing to profile transcriptome responses from cells grown under microoxic and hyperoxic conditions, we detected 8446 transcripts out of the 8462 annotated genes in the Cyanobase database. Two-thirds of the 50 most abundant transcripts are key proteins in photosynthesis. Microoxic conditions negatively affected the levels of expression of genes encoding photosynthetic complexes, with the exception of some subunits. In addition to the known regulation of the multiple copies of psbA, we detected a similar transcriptional pattern for psbJ and psbU, which might play a key role in the altered components of photosystem II. Furthermore, regulation of genes encoding proteins important for reactive oxygen species-scavenging is discussed at genome level, including, for the first time, specific small RNAs having possible regulatory roles under varying oxygen levels.

Bacterial adaptation by a transposition burst of an invading IS element

“…Evolutionary changes in cyclic diguanylate signaling have been previously shown to be central to diversification in biofilms of Pseudomonas aeruginosa ( Flynn et al 2016 ). In CCMEE 5410, peg.4655 is constitutively expressed ( supplementary table S7 , Supplementary Material online ), and its ortholog in A. marina MBIC11017 is upregulated under microoxic conditions ( Hernández-Prieto et al 2017 ). Its effector protein and the downstream consequences of its inactivation remain to be determined.…”

Structural and functional insights into the unique CBS–CP12 fusion protein family in cyanobacteria

“…1 B ) but similar to several photosynthetic Trx target proteins ( 13 – 15 , 27 , 33 ). The concerted gene expression of CBS–CP12 and TrxA is also evident in the symbiotic strain Acaryochloris marina ( 34 ), indicating they form part of an operon. In this context it is interesting to note that CBS–CP12/TrxA gene clusters are predominant in scum-forming strains that are exposed to extreme high-light conditions at the surface of lakes and in benthic mat-forming and marine symbiotic cyanobacteria.…”

Bacterial adaptation by a transposition burst of an invading IS element

“…We predicted that mutations at this locus are associated with the loss of the ability to form biofilm. The results of an adherence assay [38] demonstrated that this was indeed the case. Evolved populations with a BYK mutation produced less biofilm than either evolved populations without a BYK mutation (F1,37 = 23.6, p < 0.0001) or the ancestral population (F1,19 = 5.51, p = 0.03).…”

“…Evolutionary changes in cyclic diguanylate signaling have been previously shown to be central to diversification in biofilms of Pseudomonas aeruginosa [37]. In CCMEE 5410, peg.4655 is constitutively expressed (Supplementary file 6), and its ortholog in A. marina MBIC11017 is upregulated under microoxic conditions [38]. Its effector protein and the downstream consequences of its inactivation remain to be determined.…”