Prochlorococcus is a genus of very small (0.6 μm) marine cyanobacteria with an unusual pigmentation. These bacteria belong to the photosynthetic picoplankton and are probably the most abundant photosynthetic organism on Earth. Prochlorococcus microbes are among the major primary producers in the ocean, responsible for a large percentage of the photosynthetic production of oxygen. Prochlorococcus strains, called ecotypes, have physiological differences enabling them to exploit different ecological niches. Analysis of the genome sequences of Prochlorococcus strains show that 1,273 genes are common to all strains, and the average genome size is about 2,000 genes. In contrast, eukaryotic algae have over 10,000 genes.
The ATPC RNA motif is a conserved RNA structure found in certain cyanobacteria. It is apparently ubiquitous in Prochlorococcus marinus, and is present in many species in the genus Synechococcus. The RNA is always found within an operon encoding subunits of ATP synthase, and it is always located downstream of the gene encoding the A subunit of ATP synthase, and upstream of the C subunit gene. This location is consistent with a cis-regulatory element, but also with a non-coding RNA that is transcribed with the ATP synthase genes.
Yfr1 is a Cyanobacterial functional RNA that was identified by a comparative genome based screen for RNAs in cyanobacteria. Further analysis has shown that the RNA is well conserved and highly expressed in cyanobacteria. and is required for growth under several stress condition Bioinformatics research combined with follow-up experiments have shown that Yfr1 inhibits the translation of the proteins PMM1119 and PMM1121 by an antisense interaction by base pairing at the ribosomal binding site.
The Acido-1 RNA motif is a conserved RNA structure identified by bioinformatics. It is found only in acidobacteriota, and appears to be a non-coding RNA as it does not have a consistent association with protein-coding genes.
The Bacteroid-trp RNA motif is a conserved RNA element detected by bioinformatics. It is found in the phylum Bacteroidota in the apparent 5' untranslated regions of genes that encode enzymes used in the synthesis of the amino acid tryptophan. A short open reading frame is found within the motif that encodes at least two tryptophan codons. Similar motifs have been identified regulating tryptophan genes in Pseudomonadota, but not in Bacteroidota. However, the Bacteroid-trp RNA motif likely operates via the same mechanism of attenuation.
The Cyano-2 RNA motif is a conserved RNA structure identified by bioinformatics. Cyano-2 RNAs are found in Cyanobacterial species classified within the genus Synechococcus. Many terminal loops in the two conserved stem-loops contain the nucleotide sequence GCGA, and these sequences might in some cases form stable GNRA tetraloops. Since the two stem-loops are somewhat distant from one another it is possible that they represent two independent non-coding RNAs that are often or always co-transcribed. The region one thousand base pairs upstream of predicted Cyano-2 RNAs is usually devoid of annotated features such as RNA or protein-coding genes. This absence of annotated genes within one thousand base pairs is relatively unusual within bacteria.
The Downstream-peptide motif refers to a conserved RNA structure identified by bioinformatics in the cyanobacterial genera Synechococcus and Prochlorococcus and one phage that infects such bacteria. It was also detected in marine samples of DNA from uncultivated bacteria, which are presumably other species of cyanobacteria.
The glutamine riboswitch is a conserved RNA structure that was predicted by bioinformatics. It is present in a variety of lineages of cyanobacteria, as well as some phages that infect cyanobacteria. It is also found in DNA extracted from uncultivated bacteria living in the ocean that are presumably species of cyanobacteria.
The manA RNA motif refers to a conserved RNA structure that was identified by bioinformatics. Instances of the manA RNA motif were detected in bacteria in the genus Photobacterium and phages that infect certain kinds of cyanobacteria. However, most predicted manA RNA sequences are derived from DNA collected from uncultivated marine bacteria. Almost all manA RNAs are positioned such that they might be in the 5' untranslated regions of protein-coding genes, and therefore it was hypothesized that manA RNAs function as cis-regulatory elements. Given the relative complexity of their secondary structure, and their hypothesized cis-regulatory role, they might be riboswitches.
The wcaG RNA motif is an RNA structure conserved in some bacteria that was detected by bioinformatics. wcaG RNAs are found in certain phages that infect cyanobacteria. Most known wcaG RNAs were found in sequences of DNA extracted from uncultivated marine bacteria. wcaG RNAs might function as cis-regulatory elements, in view of their consistent location in the possible 5' untranslated regions of genes. It was suggested the wcaG RNAs might further function as riboswitches.
PhotoRC RNA motifs refer to conserved RNA structures that are associated with genes acting in the photosynthetic reaction centre of photosynthetic bacteria. Two such RNA classes were identified and called the PhotoRC-I and PhotoRC-II motifs. PhotoRC-I RNAs were detected in the genomes of some cyanobacteria. Although no PhotoRC-II RNA has been detected in cyanobacteria, one is found in the genome of a purified phage that infects cyanobacteria. Both PhotoRC-I and PhotoRC-II RNAs are present in sequences derived from DNA that was extracted from uncultivated marine bacteria.
The Polynucleobacter-1 RNA motif is a conserved RNA structure that was identified by bioinformatics. The RNA structure is predominantly located in genome sequences derived from DNA extracted from uncultivated marine samples. However it was also predicted in the genome of Polynucleobacter species QLW-P1DMWA-1, a kind of betaproteobacteria. The RNAs are often located near to a conserved gene that might be homologous to a gene found in a phage that infects cyanobacteria. However, it is unknown if the RNA is used by phages.
The psaA RNA motif describes a class of RNAs with a common secondary structure. psaA RNAs are exclusively found in locations that presumably correspond to the 5' untranslated regions of operons formed of psaA and psaB genes. For this reason, it was hypothesized that psaA RNAs function as cis-regulatory elements of these genes. The psaAB genes encode proteins that form subunits in the photosystem I structure used for photosynthesis. psaA RNAs have been detected only in cyanobacteria, which is consistent with their association with photosynthesis.
The psbNH RNA motif describes a class of RNA molecules that have a conserved secondary structure. psbNH RNAs are always found between psbH and psbH genes, both of which are involved in the cyanobacterial photosystem II are transcribed in opposite orientations. It is unknown whether the biological psbNH RNA is as depicted in the diagram, or whether its reverse complement is the transcribed molecule. In either case, the RNA would be in the 5' untranslated region of a gene, either psbN or psbH, and likely a cis-regulatory element.
The sbcD RNA motif is a conserved RNA structure identified using bioinformatics. sbc RNAs are found some species of bacteria classified under the family Burkholderiaceae, and usually reside in plasmids. They are always located in what might be the 5' untranslated regions of operons that include sbcD genes. sbcD genes are involved in DNA repair.
PtaRNA1 is a family of non-coding RNAs. Homologs of PtaRNA1 can be found in the bacterial families, Betaproteobacteria and Gammaproteobacteria. In all cases the PtaRNA1 is located anti-sense to a short protein-coding gene. In Xanthomonas campestris pv. vesicatoria, this gene is annotated as XCV2162 and is included in the plasmid toxin family of proteins.
Bacterial small RNAs (bsRNA) are small RNAs produced by bacteria; they are 50- to 500-nucleotide non-coding RNA molecules, highly structured and containing several stem-loops. Numerous sRNAs have been identified using both computational analysis and laboratory-based techniques such as Northern blotting, microarrays and RNA-Seq in a number of bacterial species including Escherichia coli, the model pathogen Salmonella, the nitrogen-fixing alphaproteobacterium Sinorhizobium meliloti, marine cyanobacteria, Francisella tularensis, Streptococcus pyogenes, the pathogen Staphylococcus aureus, and the plant pathogen Xanthomonas oryzae pathovar oryzae. Bacterial sRNAs affect how genes are expressed within bacterial cells via interaction with mRNA or protein, and thus can affect a variety of bacterial functions like metabolism, virulence, environmental stress response, and structure.
In molecular biology, Cyanobacterial non-coding RNAs are non-coding RNAs which have been identified in species of cyanobacteria. Large scale screens have identified 21 Yfr in the marine cyanobacterium Prochlorococcus and related species such as Synechococcus. These include the Yfr1 and Yfr2 RNAs. In Prochlorococcus and Synechocystis, non-coding RNAs have been shown to regulate gene expression. NsiR4, widely conserved throughout the cyanobacterial phylum, has been shown to be involved in nitrogen assimilation control in Synechocystis sp. PCC 6803 and in the filamentous, nitrogen-fixing Anabaena sp. PCC 7120.
Genomic streamlining is a theory in evolutionary biology and microbial ecology that suggests that there is a reproductive benefit to prokaryotes having a smaller genome size with less non-coding DNA and fewer non-essential genes. There is a lot of variation in prokaryotic genome size, with the smallest free-living cell's genome being roughly ten times smaller than the largest prokaryote. Two of the bacterial taxa with the smallest genomes are Prochlorococcus and Pelagibacter ubique, both highly abundant marine bacteria commonly found in oligotrophic regions. Similar reduced genomes have been found in uncultured marine bacteria, suggesting that genomic streamlining is a common feature of bacterioplankton. This theory is typically used with reference to free-living organisms in oligotrophic environments.
Microbial DNA barcoding is the use of DNA metabarcoding to characterize a mixture of microorganisms. DNA metabarcoding is a method of DNA barcoding that uses universal genetic markers to identify DNA of a mixture of organisms.
