## 2 Results
### Identification of VOCs from Bacillus sp. BO53 and Pseudoalteromonas sp. GA327  
The analysis for identification of VOCs biosynthesized by octocoral-associated bacteria _Bacillus_ sp. BO53 and _Pseudoalteromonas_ sp. GA327 was performed by HS-SPME-GC-MS technique. Each marine bacteria sample was analyzed three times using the DVB/CAR/PDMS coating solid-phase microextraction fiber; 37 \({}^{\circ}\)C extraction temperature; and 40 min extraction time. DVB/CAR/PDMS fiber was selected due to its high capacity for the extraction of volatile and semi-volatile compounds present in samples [21; 22; 23]. In total, 19 bVOCs were identified, of which 11 were detected in _Bacillus_ sp. BO53 and 13 in _Pseudoalteromonas_ sp. GA327 (Table 2). Compounds that were present in the blank Luria Bertani (LB) broth, supplemented with seawater, were excluded. Ketone comprised the largest compounds detected in _Bacillus_ sp. BO53, followed by alcohols, sesquiterpenes, monoterepenes, aromatics, and alkanes (Figure 1a). 5-Acetyl-2-methylpyridine (64.63%), 2-butanone (17.03%), and 2-nonanone (7.00%) were the major VOCs detected in _Bacillus_ sp. BO53. In the case of _Pseudoalteromonas_ sp. GA327, alcohols are the main compounds detected followed by ketones, ester, and monoterepne compounds (Figure 1b). 1-Pentanol (38.91%), 2-butanone (20.14%), and butyl formate (17.30%) were the primary VOCs detected in _Pseudoalteromonas_ sp. GA327. 2,4-trimethylpentane, o-xylene, 5-acetyl-2-methylpyridine, \(\alpha\)-cubebene, 1-undecanol, and \(\alpha\)-longcylene are the specific VOCs produced by _Bacillus_ sp. BO53 (Figure 2b); while 1-butanol, 2-pentanone, butyl formate, 2-heptanone, 6-methyl-5-heptene-2-one, benzyl alcohol, 2-decanone, 2-undecanone were found only in _Pseudoalteromonas_ sp. GA327 (Figure 2c). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Species**} & \multirow{2}{*}{**Strain**} & \multicolumn{2}{c}{_Bacillus_ sp. **BO53**} & \multicolumn{2}{c}{_Pseudoalteromonas_ sp. **GA327**} \\ \cline{3-6}  & & **24 h** & **48 h** & **24 h** & **48 h** \\ \hline _A. baumanni_ & ATCC 19606 & - & \(\pm\) & + & + \\ \hline _S. aureus_ & ATCC 43300 & - & \(\pm\) & - & - \\ \hline _P. aeruginosa_ & ATCC 10145 & - & + & \(\pm\) & + \\ \hline \hline \end{tabular} (+) Growth inhibition; (\(\pm\)) Growth reduction; (-) No inhibition.  
\end{table} 
Table 1: Antibacterial effect of _Bacillus_ sp. and _Pseudoalteromonas_ sp. volatile compounds against _Acinetobacter baumanni_, _Staphylococcus aureus_, and _Pseudomonas aeruginosa_ pathogenic bacteria. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{5}{c}{**\% Detected Compound on Each Species**} \\ \hline \hline \multirow{2}{*}{**Compound**} & \multirow{2}{*}{**TRI**} & \multirow{2}{*}{**ERI**} & \multicolumn{2}{c}{_Bacillus_ sp.**} & \multirow{2}{*}{_Pseudoalteromonas_ sp. **GA327**} \\  & & & **BO53** & & \\ \hline
2-Butanone & 602 & 609 & 17.03 & 20.14 \\
1-Butanol & 671 & 676 & - & 4.55 \\
2,2,4-Trimethylpentane & 680 & 687 & 0.46 & - \\
2-Pentanone & 687 & 693 & - & 1.29 \\
1-Pentanol & 775 & 780 & 1.33 & 38.91 \\ Butyl formate & 787 & 793 & - & 17.30 \\ o-Xylene & 884 & 891 & 0.47 & - \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Identified mVOCs produced by the marine bacteria _Bacillus_ sp. BO53 and Pseudoalteromonas sp. GA327.