Molecular characterization and bioactive potential of newly identified strains of the extremophilic black yeast Hortaea werneckii isolated from Red Sea mangrove

Figures & data

Table 1. Pathogenic bacterial strains used in antibacterial activity assay.

Pathogenic bacteria	Bacteriology collection	Gram staining
Streptococcus pneumoniae	ATCC-49619	+
Methicillin-resistant Staphylococcus aureus (MRSA)	ATCC-33591	+
Listeria monocytogens	ATCC-BAA751	+
Enterococcus faecalis	ATCC-29212	+
Salmonella typhimurium	ATCC-13311	-
Campylobacter jejuni	ATCC-33291	-
Klebsiella pneumoniae	ATCC-13883	-
Shigella sonnei	ATCC-25931	-
Haemophilus influenzae	ATCC-10211	-
Pseudomonas aeruginosa	ATCC-27853	-

Figure 1. Culture morphology of H. werneckii MF135 (A), MF140 (B) and MF145 (C) isolates.

Figure 2. H. werneckii in 3-week-old culture. Different shapes of budding conidia and pseudomycelium (A–E).

Note: Bright-field light micrographs (mounted in water). Scale bars: 0.5 µm (A–D), 0.1 µm (E).

Figure 3. Bayesian phylogenetic tree of Hortaea spp. and related taxa, based on the nucleotide sequences of the large subunit (LSU) rDNA sequence. Numbers are bootstrap support, Maximum parsimony (MP). The H. werneckii isolates are highlighted.

Figure 4. Agar disc diffusion method using MF135 crude extract against MRSA (A), C. jejuni (B) and S. typhimurium (C).

Table 2. Preliminary bioactivity of crude extracts from H. werneckii strains against tested pathogenic bacteria (disc 5 mm).

	Inhibition zone (mm)
H. werneckii strains Pathogens	MF135	MF140	MF141
C. jejuni	24	14	18
MRSA	27	12	14
L. monocytogens	Negative	Negative	Negative
S. sonnei	7	Negative	Negative
S. typhimurium	20	16	12
S. pneumoniae	Negative	Negative	Negative
K. pneumoniae	Negative	Negative	Negative
P. aeruginosa	Negative	Negative	7
E. faecalis	6	Negative	Negative
H. influenzae	8	Negative	Negative

Table 3. Preliminary bioactivity of H. werneckii extract fractions against tested pathogenic bacteria.

	Inhibition zone (mm)
	MF135	MF140	MF141
H. werneckii strains Pathogens	Fraction 6	Fraction 3	Fraction 6
MRSA	23	11	12
C. jejuni	20	12	15
S. typhimurium	17	15	13

Figure 5. Illustration of two-fold micro-dilution plate to determine the MIC of the selected three active fractions of H. werneckii MF135, MF140 and MF141. Positive control, ciprofloxacin (3 µg/mL); Negative control, acetone.

Figure 6. GC-MS chromatogram for active fractions of H. werneckii MF135 (A), MF140 (B) and MF141 (C).

Table 4. GC-MS analysis of active fractions from H. werneckii ethyl acetate.

Fraction number	Time (min)	Compound	Formula	Molecular weight (g/mol)
MF135 Fraction 6	5.35	4-Acetoxy-2-azetidinone	C5H7NO3	129
	8.27	2,5-Methano-2H-furo[3,2-b]pyran-8-one, hexahydro-	C8H10O3	154
	11.48	sec-Butyl nitrite	C4H9NO2	103
MF140 Fraction 3	5.39	1-Propanamine, N,2-dimethyl-N-nitroso-	C5H12N2O	116
	6.072	N-carbobenzyloxy-cysteinylcysteine	C14H18N2O5S2	358
	8.333	9-Oxabicyclo[6.1.0]nonan-4-one	C8H12O2	140
	11.553	sec-Butyl nitrite	C4H9NO2	103
	13.867	Undefined long alkyl chain	C19H30O2	290
	18.362	3,6-Octadecadiynoic acid, methyl ester	C19H30O2	290
	35.835	3-Methyl-1,2-diazirine	C2H4N2	56
	37.145	Undefined long alkyl chain	C19H30O2	290
	38.525	Undefined long alkyl chain	C19H30O2	290
	39.992	Undefined long alkyl chain	C19H30O2	290
	41.502	2,4,6,8-Tetramethyl-1-undecene	C15H30	210
MF141 Fraction 6	6.623	3-Methyl-1,2-diazirine	C2H4N2	56
	34.24	Aspidofractinin-3-ylmethanol	C20H26N2O	310

Data availability

The authors confirm that the data supporting the findings of this study are available within the article.