Novel Plasmids from Environmental Acinetobacter sp

Acinetobacter sp. is a Gram-negative bacteria naturally found on soil and aquatic environments.  These bacteria can survive for extensive periods in both dry and moist surfaces bolstered with its ability to colonize in a wide range of temperatures and pH values. In the past 20 years, Acinetobacter spp. particularly A. baumanii has become an epidemic in hospitals worldwide, rendering many antibiotics from different classes ineffective. Although Acinetobacter sp. is an important pathogen, limited information is available on their plasmids, as only five species out of the total 32 species in the genus (15%) are known to carry plasmids, most of them found in A. baumanii. It was hypothesized that the environment serves as a reservoir for plasmids in Acinetobacter spp. The objective of this study was to analyze and classify two novel plasmids found on environmental Acinetobacter sp. MALDI-TOF MS was used to identify Acinetobacter sp. SW0698R. The plasmids were isolated using Qiagen Midi kit and sequenced using Illumina Next Generation Sequencing. Plasmid sequences were assembled into two contigs by Geneious Software composed of complete sequences of two plasmids (7,217 bp and 98,055 bp plasmids). Annotations were carried out by comparison with sequences in the National Center for Biotechnology Information (NCBI) database and Rapid Annotation using Subsystem Technology (RAST). Initial database searches using the Acinetobacter sp. plasmid sequences as a query indicated low identity with other plasmids suggesting that SW0698R had two novel plasmids. Furthermore, plasmids were characterized based on Rep protein sequence similarity. Molecular Evolutionary Genetics Analysis (MEGA) Software was used to create a replicon typing phylogenetic tree based on the characterized plasmids in A. baumannii. Plasmid 7,217 bp carried highly related replicons to plasmids in the GR8 group, while plasmid 98,055 bp remained uncategorized. Plasmid 7,217 bp contains 10 predicted coding sequences (8 hypothetical proteins, a replicase, and a MobA/L Protein) with GC content of 33%. The presence of mob genes in plasmid 7,217 bp suggests this plasmid is mobilizable. Plasmid 98,055 bp had 146 CDS with a total of 24 (16%) encoding for mobile elements (22 transposases and 2 Tn7 transposition proteins), 4 (2%) encoding putative virulence proteins (Gifsy-2 prophage Lysozyme and HipA toxin), and 28 (19%) encoding cytosolic proteins with GC content of 38.9%. No mob or tra genes were found in plasmid 98,055 bp. Two novel plasmids were discovered from environmental Acinetobacter sp., further investigation is needed to know the function of each gene in the plasmids and potential threats of plasmid dissemination to other bacteria.