# Evaluating the antibacterial properties of deep-sea sponges Dactylospongia elegants, Stelletta fibrosa, and Haliclona manglaris from the Jordanian Gulf of Aqaba

## TL;DR

This study explores antibacterial properties of three deep-sea sponges from the Jordanian Gulf of Aqaba, finding that Dactylospongia elegans shows strong potential against antibiotic-resistant bacteria.

## Contribution

The study identifies Dactylospongia elegans as a new source of potent antibacterial compounds from deep-sea sponges.

## Key findings

- Dactylospongia elegans showed inhibition zones of 6-21 mm against Gram-positive bacteria.
- LC-MS/MS analysis detected bioactive compounds like gallic acid and dactyloquinone in D. elegans.
- The sponge's extracts had low MIC/MBC values (0.25-3 mg/ml), indicating strong antibacterial activity.

## Abstract

Marine sponges are known for their rich variety of secondary metabolites, many of which show potential for pharmaceutical applications. In this study, three deep-sea sponge species—Stelletta fibrosa, Dactylospongia elegans, and Haliclona manglaris—were identified using DNA barcoding, and their ethanolic extracts were tested for antibacterial activity. The extracts were evaluated against Gram-positive (e.g., Bacillus pumilus, Staphylococcus aureus, Staphylococcus epidermidis, and methicillin-resistant Staphylococcus aureus, MRSA) and Gram-negative bacteria (e.g., Escherichia coli and Klebsiella aerogenes) using the agar well diffusion method. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were also determined. Among the extracts, D. elegans exhibited the most potent antibacterial activity, with inhibition zones ranging from six to 21 mm against gram-positive bacteria and low MIC/MBC values from 0.25 to three mg/ml. Liquid chromatography-mass spectrometry (LC-MS/MS) analysis of D. elegans revealed the presence of bioactive compounds such as gallic acid, caffeic acid, bolinaquinone, dactyloquinone, and others, which are known for their antimicrobial properties. These findings suggest that D. elegans has promising antibacterial properties that could be valuable in combating antimicrobial resistance.