Bacterial biofilm can cause nosocomial recurrent infections and implanted device secondary infections in patients and strongly promotes development of pathogenic drug resistance in clinical treatments. Butenolide is an effective anti-macrofouling compound derived from a marine Streptomyces sp., but its antibiofilm efficacy remains largely unexplored. In the present study, the antibiofilm activities of butenolide were examined using biofilms formed by both Gram-positive and Gram-negative pathogenic model species. Four Escherichia coli strains, Pseudomonas aeruginosa , and methicillin-resistant Staphylococcus aureus (MRSA) were used as targets in antibiofilm assays that examined the effects of butenolide, including the following: (i) on bacterial growth; (ii) in inhibiting biofilm formation and eradicating mature biofilm; (iii) on biofilm structures. In addition, the synergistic effect between butenolide with tetracycline was also examined. Butenolide not only effectively inhibited the biofilm formation but also eradicated pre-formed biofilms of tested bacteria. Fractional inhibitory concentration index (FICI) indicated that butenolide was a potential tetracycline enhancer against E. coli , P. aeruginosa , and MRSA. These results indicated that butenolide may hold a great potential as an effective antibiofilm agent to control and prevent biofilm-associated infections in future clinical treatments. Electronic supplementary material The online version of this article (10.1007/s10126-018-9861-1) contains supplementary material, which is available to authorized users.

An aerobic, Gram-stain-negative, rod-shaped and non-motile strain (XY-359T) was isolated from the mouth of a marine invertebrate Onchidium species from the South China Sea. It grew at pH 6.0–8.5 (optimum, pH 7.5), at 15−37 °C (optimum, 30 °C) and in the presence of 0.5–4.5 % (w/v) NaCl (optimum, 2.5 %). It could not hydrolyse Tweens 20, 40, 60 or 80 and no flexirubin-type pigments were produced. The major polar lipids were phosphatidylethanolamine, one unidentified aminolipid, six unidentified phospholipids and two unidentified polar lipids. The major fatty acids were iso-C17:0 3-OH, iso-C15:1 G and iso-C15:0 3-OH. The respiratory quinone was MK-6. Strain XY-359T showed the greatest degree of 16S rRNA sequence similarity to Flagellimonas algicola AsT0115T (96.54 %), followed by Muricauda flava DSM 22638T (96.27 %). Phylogenetic analysis based on 16S rRNA gene sequences and 31 core genes indicated that strain XY-359T belongs to the genus Muricauda . The genome size of strain XY-359T was 4 207 872 bp, with 39.1 mol% of DNA G+C content. The average nucleotide identity and digital DNA–DNA hybridization values between strain XY-359T and F. algicola AsT0115T were 74.58 % and 18.5 %, respectively, and those between strain XY-359T and M. flava DSM 22638T were 74.2 % and 18.3 %. The combined phenotypic, chemotaxonomic and phylogenetic data suggest that strain XY-359T represents a novel species of the genus Muricauda , for which the name Muricauda onchidii sp. nov. is proposed. The type strain is XY-359T (=MCCC 1K03658T =KCTC 72218T). Moreover, based on the proposal of nesting Spongiibacterium and Flagellimonas within Muricauda by García (Validation List No. 193) and the analyses of phylogenetic trees and average amino acid identities in this study, the transfers of F. algicola , F. pacifica and F. maritima to the genus Muricauda as Muricauda algicola comb. nov., Muricauda parva nom. nov. and M. aurantiaca nom. nov., respectively, are proposed, with an emended description of the genus Muricauda .

A novel bacterial strain, XY-99T, was isolated from the epidermis of a marine invertebrate of the genus Onchidium from seawater of the South China Sea. The cells of the strain were aerobic, Gram-stain-negative, non-motile, and oval-shaped (0.8–1.0 µm wide and 1.0–1.5 µm long) without a flagellum. The strain grew at temperatures of 15–37 °C (optimum, 35–37 °C), at pH 5.5–9.5 (optimum 7.5), and at NaCl concentrations of 0–12.0 % (w/v) (optimum 1.5–3.0 %). The major fatty acids (>10 %) were summed feature 8 (comprising C18 : 1ω7c and/or C18 : 1ω6c), C16 : 0 and 11-methyl C18 : 1ω7c. The predominant polar lipid was diphosphatidylglycerol. The respiratory quinone was Q-10. The closet phylogenetic neighbours were Pseudooceanicola flagellatus DY470T and Pseudooceanicola nitratireducens JLT1210T, showing 97.5 and 97.3 % of 16 s rRNA gene sequence similarity. The genome size of XY-99T was 3 673 499 bp, with 64.5 % DNA G+C content. The average nucleotide identity and digital DNA–DNA hybridization values between XY-99T and Pseudooceanicola flagellatus DY470T were 72.8 and 14.0 %, respectively, while they were 79.3 and 22.3 % between XY-99T and Pseudooceanicola nitratireducens JLT1210T. Characterization based on phylogenetic, phenotypic, chemotaxonomic and genomic evidence demonstrated that XY-99T represents a novel species of the genus Pseudooceanicola , for which the name Pseudooceanicola onchidii sp. nov. is proposed. The type strain is XY-99T (=KCTC 72211T=MCCC 1K03607T).

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A novel bacterial strain, J103, was isolated from rhizosphere soil of the mangrove plant Kandelia in Mai Po Inner Deep Bay Ramsar Site, Hong Kong. The strain was aerobic, Gram-stain-negative, oval-shaped with folds in the middle, non-motile and non-spore-forming. It grew at temperatures of 20-30 °C (optimum, 25-30 °C), at pH 6.0-9.0 (optimum pH 6.0) and at NaCl concentrations of 0.5-5.0 % (w/v) (optimum 1.0-2.0 %). Strain J103 was able to reduce nitrate to nitrite, and hydrolyse urea, Tween 40 and Tween 60. The major polar lipids were aminolipid, glycolipid, phosphatidylcholine and phosphatidylglycerol. The major fatty acids were C18 : 1ω7c and C19 : 0 cyclo ω8c. The respiratory quinone was Q-10. The DNA G+C content was 68.5 mol%. Sequence analysis of the 16S rRNA gene indicated that strain J103 belongs to the genus Acuticoccus, within the family Rhodobacteraceae. The closest phylogenetic neighbour was Acuticoccus yangtzensis JL1095, showing 96.2 % 16S rRNA gene sequence similarity. The genome size of strain J103 was 6 478 100 bp. The average nucleotide identity and digital DNA-DNA hybridization values between strain J103 and Acuticoccus yangtzensis JL1095 were 75.44 and 16.43 %, respectively. Characterization based on phylogenetic, phenotypic, chemotaxonomic and genomic evidence demonstrated that strain J103 represents a novel species of the genus Acuticoccus, for which the name Acuticoccus kandeliae sp. nov. is proposed. The type strain is J103 (=DSM 104434=MCCC 1K03288).