# Comparative Genomics of Genes for rhamnolipid synthesis and monoaromatic hydrocarbon tolerance in environmental strains of Pseudomonas aeruginosa

## TL;DR

This study uses comparative genomics to explore how Pseudomonas aeruginosa strains from polluted environments handle hydrocarbons and heavy metals.

## Contribution

The study reveals new insights into the genomic organization of rhl and mla genes in Pseudomonas aeruginosa strains from hydrocarbon-polluted sites.

## Key findings

- All strains had a double copy of the rhlB gene with consistent gene organization.
- Most strains had two copies of mlaA, mlaFEDC, and mlaEFD genes for toluene tolerance.
- P. aeruginosa strains showed high synteny in mla gene blocks but distinct arrangements compared to P. putida.

## Abstract

Aromatic hydrocarbons such as Benzene, Toluene, Ethylbenzene and Xylene (BTEX), give us an environmental challenge. They can be degraded by strains of
Pseudomonas aeruginosa, through emulsification (
rhl genes) and biodegradation processes. The BTEX tolerance genes (
mlaABCD) may be present in it. The aim of this research was to evaluate, through comparative genomics, the genes of the
rhl and
mla systems in six strains isolated from hydrocarbon polluted environments.

This study examines six Pseudomonas aeruginosa strains isolated from hydrocarbon-contaminated sites in Peru. Each strain shows capabilities like hydrocarbon degradation and heavy metal tolerance. After DNA extraction, sequencing, and quality-controlled assembly, functional genome annotation was performed using BAKTA. Comparative analysis included high-quality
Pseudomonas genomes from RefSeq, with ANI metrics to assess genetic similarity. A phylogenetic tree, built from core gene alignment, reveals evolutionary connections and was visualized with iTOL.

Results showed that all strains had a double copy of the
rhlB gene, arranged in the same organization, with
rhlABRI genes always adjacent in a 3′-5′ direction. However,
rhlG varied in position and orientation among strains, often near
rhlC. The C1BHIC5 strain had only one copy of the rhlB gene, and the 3′ – 5 orientation of the
rhlG gene was the exception. Most strains had two copies of
mlaA,
mlaFEDC, and
mlaEFD genes for toluene tolerance, with diverse orientations across strains. High synteny was noted within
mla gene blocks. Compared to
Pseudomonas putida, where
mla genes are positioned between
murA and
ppcD with an additional toluene tolerance gene (
ttg2D), strains of
P. aeruginosa strains display a similar yet distinct gene arrangement.

In conclusion, the presence of the
rhlABC genes in all the strains analyzed and the BTEX tolerance genes allowed us to understand the great ability of
P. aeruginosa to survive in polluted environments.