A pan-genomic assessment: Delving into the genome of the marine epiphyte Bacillus altitudinis strain 19_A and other very close Bacillus strains from multiple environments.

Marine macroalgae are the habitat of epiphytic bacteria and provide several conditions for a beneficial biological interaction to thrive. Although Bacillus is one of the most abundant epiphytic genera, genomic information on marine macroalgae-associated Bacillus species remains scarce. In this study, we further investigated our previously published genome of the epiphytic strain Bacillus altitudinis 19_A to find features that could be translated to potential metabolites produced by this microorganism, as well as genes that play a role in its interaction with its macroalgal host. To achieve this goal, we performed a pan-genome analysis of Bacillus sp. and a codon bias assessment, including the genome of the strain Bacillus altitudinis 19_A and 29 complete genome sequences of closely related Bacillus strains isolated from soil, marine environments, plants, extreme environments, air, and food. This genomic analysis revealed that Bacillus altitudinis 19_A possessed unique genes encoding proteins involved in horizontal gene transfer, DNA repair, transcriptional regulation, and bacteriocin biosynthesis. In this comparative analysis, codon bias was not associated with the habitat of the strains studied. Some accessory genes were identified in the Bacillus altitudinis 19_A genome that could be related to its epiphytic lifestyle, as well as gene clusters for the biosynthesis of a sporulation-killing factor and a bacteriocin, showing their potential as a source of antimicrobial peptides. Our results provide a comprehensive view of the Bacillus altitudinis 19_A genome to understand its adaptation to the marine environment and its potential as a producer of bioactive compounds.

Genome of the epiphytic bacterium Achromobacter denitrificans strain EPI24, isolated from a macroalga located in the Colombian Caribbean.

Marine macroalgae are being recognized as reservoirs of biologically active compounds, as their surfaces are susceptible to the colonization of microorganisms which can produce enzymes with a wide range of molecular architectures. Among these bacteria, Achromobacter is responsible for the biosynthesis of laccases. In this research, we performed a bioinformatic pipeline to annotate the sequenced complete genome of the epiphytic bacterium Achromobacter denitrificans strain EPI24, from the macroalgal surface of the Ulva lactuca species; this strain showed laccase activity which has been previously assessed on plate assays. The genome of A. denitrificans strain EPI24 has a size of ∼6.95 Mb, a GC content of 67.33%, and 6,603 protein-coding genes. The functional annotation of the A. denitrificans strain EPI24 genome confirmed the presence of genes encoding for laccases, which could have functional properties of interest in processes such as the biodegradation of phenolic compounds under versatile and efficient conditions.

Genome sequence of the epiphytic bacteria Bacillus altitudinis strain 19_A, isolated from the marine macroalga Ulva lactuca.

Microorganisms living on marine macroalgal surfaces require enzyme repertoires to metabolize macroalgal-synthesized compounds. These enzymes are biological catalysts which have specific functional properties for biotechnological applications. Here, we raise awareness on the set of enzyme categories produced by the Bacillus altidudinis strain 19_A, isolated from the marine macroalga Ulva lactuca, as revealed by the analysis of its complete genome sequence. The genome of B. altitudinis strain 19_A is ∼3.7 Mb long, has a G + C content of 41.2 %, and contains a total of 3,967 protein-coding genes. Our predictive analysis revealed that these genes encode proteases, lipases, esterases, and enzymes involved in the synthesis, degradation, and modification of carbohydrates. This enzyme repertoire may have promising biotechnological and industrial applications.

Temporal Changes of the Epiphytic Bacteria Community From the Marine Macroalga Ulva lactuca (Santa Marta, Colombian-Caribbean).

Microbial communities live on macroalgal surfaces. The identity and abundance of the bacteria making these epiphytic communities depend on the macroalgal host and the environmental conditions. Macroalgae rely on epiphytic bacteria for basic functions (spore settlement, morphogenesis, growth, and protection against pathogens). However, these marine bacterial-macroalgal associations are still poorly understood for macroalgae inhabiting the Colombian Caribbean. This study aimed at characterizing the epiphytic bacterial community from macroalgae of the species Ulva lactuca growing in La Punta de la Loma (Santa Marta, Colombia). We conducted a 16S rRNA gene sequencing-based study of these microbial communities sampled twice a year between 2014 and 2016. Within these communities, the Proteobacteria, Bacterioidetes, Cyanobacteria, Deinococcus-Thermus and Actinobacteria were the most abundant phyla. At low taxonomic levels, we found high variability among epiphytic bacteria from U. lactuca and bacterial communities associated with macroalgae from Germany and Australia. We observed differences in the bacterial community composition across years driven by abundance shifts of Rhodobacteraceae Hyphomonadaceae, and Flavobacteriaceae, probably caused by an increase of seawater temperature. Our results support the need for functional studies of the microbiota associated with U. lactuca, a common macroalga in the Colombian Caribbean Sea.