Artemisia herba-alba (AHA), known as sheeh in Jordan, is recommended by regional traditional healers for the treatment of a variety of diseases. AHA has been used in folk medicine to treat colds, coughing, bronchitis, intestinal disturbances, diarrhea, neuralgias, arterial hypertension, and diabetes. The objectives of the current study were to identify the chemical compositions of the essential oil extracted from dried leaf powder of AHA cultivated in Jordan and investigate its antibacterial and antioxidant activities. The essential oil was isolated using hydro distillation, and the identification of artemisia herba-alba essential oil (AHEO) composition was performed using validated gas chromatography-mass spectrometry (GC-MS). The antibacterial activity of AHEO was assessed against escherichia coli, pseudomonas aeruginosa, klebsiella pneumonia, and staphylococcus aureus and two clinical isolates (methicillin-resistant staphylococcus aureus and methicillin-resistant staphylococcus epidermidis [MRSE]) using a disc diffusion method, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) values, using the micro-dilution broth method. Additionally, antioxidant activities were determined using DPPH and ABTS radical scavenging assays. The results revealed that the yield of AHEO was 4.41% v/w, with nearly 22 identified compounds, constituting approximately 96.80% of the total mass of essential oils. Monoterpenoids was the major compounds (71.90%), with alpha pinene being the major component, accounting for 17.20% of the composition. The total phenolic and flavonoid contents were 43.97 mg GAE/g and 30.11 mg CE/g, respectively. The antibacterial activity of AHEO against MRSE exhibited the highest inhibitory effect, while E.coli showed the highest MBC value. Furthermore, AHEO demonstrated significant antioxidant activity (IC50= 64.57 and 34.01 for DPPH and ABTS, respectively). The results indicate that AHEO possess good antioxidant and antibacterial properties, suggesting that they may be used as a supplementary food and antimicrobial agent.

The ability to metabolize sucrose is a variable trait within the family Vibrionaceae. The marine bacterium Photobacterium damselae subsp. damselae (Pdd), pathogenic for marine animals and humans, is generally described as negative for sucrose utilization (Scr⁻). Previous studies have reported sucrose-utilizing isolates (Scr⁺), but the genetic basis of this variable phenotype remains uncharacterized. Here, we carried out the genome sequencing of five Scr⁺ and two Scr⁻Pdd isolates and conducted a comparative genomics analysis with sixteen additional Pdd genomes sequenced in previous studies. We identified two different versions of a four-gene cluster (scr cluster) exclusive of Scr⁺ isolates encoding a PTS system sucrose-specific IIBC component (scrA), a fructokinase (scrK), a sucrose-6-phosphate hydrolase (scrB), and a sucrose operon repressor (scrR). A scrA deletion mutant did not ferment sucrose and was impaired for growth with sucrose as carbon source. Comparative genomics analyses suggested that scr clusters were acquired by horizontal transfer by different lineages of Pdd and were inserted into a recombination hot-spot in the Pdd genome. The incongruence of phylogenies based on housekeeping genes and on scr genes revealed that phylogenetically diverse gene clusters for sucrose utilization have undergone extensive horizontal transfer among species of Vibrio and Photobacterium.

The marine bacterium Photobacterium damselae subsp. piscicida (Pdp) causes photobacteriosis in fish and important financial losses in aquaculture, but knowledge of its virulence factors is still scarce. We here demonstrate that an unstable plasmid (pPHDPT3) that encodes a type III secretion system (T3SS) is highly prevalent in Pdp strains from different geographical origins and fish host species. We found that pPHDPT3 undergoes curing upon in vitro cultivation, and this instability constitutes a generalized feature of pPHDPT3-like plasmids in Pdp strains. pPHDPT3 markers were detected in tissues of naturally-infected moribund fish and in the Pdp colonies grown directly from the fish tissues but were undetectable in a fraction of the colonies produced upon the first passage of the primeval colonies on agar plates. Notably, cured strains exhibited a marked reduction in virulence for fish, demonstrating that pPHDPT3 is a major virulence factor of Pdp. The attempts to stabilize pPHDPT3 by insertion of antibiotic resistance markers by allelic exchange caused an even greater reduction in virulence. We hypothesize that the existence of a high pressure to shed pPHDPT3 plasmid in vitro caused the selection of clones with off-target mutations and gene rearrangements during the process of genetic modification. Collectively, these results show that pPHDPT3 constitutes a novel, hitherto unreported virulence factor of Pdp that shows a high instability in vitro and warn that the picture of Pdp virulence genes has been historically underestimated, since the loss of the T3SS and other plasmid-borne genes may have occurred systematically in laboratories for decades.

Here, we report the draft genome sequences of two strains of the fish pathogen Photobacterium damselae subsp. piscicida , isolated from Salmo salar (SNW-8.1) and Seriola quinqueradiata (PP3). The identification of a type III secretion system in the two genomes furthers our understanding of the pathobiology of this subspecies.