Biofouling causes major problems and economic losses to marine and shipping industries. In the search for new antifouling agents, marine bacteria with biosurfactants production capability can be an excellent option, due to the amphipathic surface-active characteristic that confers antimicrobial and antibiofilm activities. The aim of this study was to evaluate the antifouling activity of biosurfactants producing marine bacteria from the Gulf of California. The cell free culture supernatant (CFCS) of Bacillus niabensis (S-69), Ralstonia sp. (S-74) (isolated from marine sediment) and of B. niabensis (My-30) (bacteria associated to the sponge Mycale ramulosa) were screened for production of biosurfactants (using hemolysis and drop collapse test, oil displacement and emulsifying activity). The toxicity and antifouling activity were evaluated against biofoulers (bacteria forming biofilm and macrofoulers) both in laboratory and field assays. The results indicate that all bacteria were biosurfactant producers, but the higher capability was shown by B. niabensis (My-30) with high emulsifying properties (E24) of 71%. The CFCS showed moderate toxicity but were considered non-toxic against Artemia franciscana at low concentrations. In the antifouling assay, the CFCS of both strains of B. niabensis showed the best results for the reduction of the biofilm formation (up 50%) against all Gram-positive bacteria and most Gram-negative bacteria with low concentrations. In the field assay, the CFCS of B. niabensis (My-30) led to the reduction of 30% of biofouling compared to the control. The results indicate that the biosurfactant produced by B. niabensis (My-30) has promising antifouling activity.

Marine obligate actinobacteria produce a wide variety of secondary metabolites with biological activity, notably those with antibiotic activity urgently needed against multi-drug-resistant bacteria. Seventy-five marine actinobacteria were isolated from a marine sediment sample collected in Punta Arena de La Ventana, Baja California Sur, Mexico. The 16S rRNA gene identification, Multi Locus Sequence Analysis, and the marine salt requirement for growth assigned seventy-one isolates as members of the genus Salinispora, grouped apart but related to the main Salinispora arenicola species clade. The ability of salinisporae to inhibit bacterial growth of Staphylococcus epidermidis, Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacer baumannii, Pseudomonas aeruginosa, and Enterobacter spp. was evaluated by cross-streaking plate and supernatant inhibition tests. Ten supernatants inhibited the growth of eight strains of S. epidermidis from patients suffering from ocular infections, two out of the eight showed growth inhibition on ten S. epidermidis strains from prosthetic joint infections. Also, it inhibited the growth of the remaining six multi-drug-resistant bacteria tested. These results showed that some Salinispora strains could produce antibacterial compounds to combat bacteria of clinical importance and prove that studying different geographical sites uncovers untapped microorganisms with metabolic potential.

Orchid root-associated fungal endophytes (ORAFEs) represent an important component of fungal biodiversity with potential applications in orchid conservation and sustainable production. ORAFEs were isolated from the roots of four orchid species in Veracruz, Mexico: Gongora galeata, Maxillaria densa, Maxillaria tenuifolia, and Maxillaria variabilis to investigate their diversity and plant-growth-promoting (PGP) properties. Taxonomic identification relied on morphological and molecular phylogenetic analyses using ITS, TEF1-α, β-tubulin (TUB2), and actin (ACT). Fifty-six isolates were grouped into 20 morphotypes representing 15 genera, including Aspergillus, Biscogniauxia, Chaetomium, Colletotrichum, Thelonectria, Diaporthe, Fusarium, Geotrichum, Hypoxylon, Lasiodiplodia, Mucor, Periconia, Pestalotiopsis, Trichoderma, Xylaria, and two isolates that may represent undescribed taxa requiring further polyphasic taxonomic investigation. Functional experiments indicated a wide range of PGP activities: ten strains solubilized phosphate, eight produced siderophores, twelve synthesized indole-3-acetic acid, fourteen produced pectinases, six fungi exhibited antibacterial activity against Bacillus subtilis, and five inhibited Staphylococcus aureus. Furthermore, Trichoderma atroviride TR1-T2 and Xylaria multiplex XY1-D42 showed antagonistic activity against Phytopythium vexans, characterized by a contact-dependent displacement effect. Five strains were chosen for further research as orchid bioinoculants based on their PGP and antagonistic traits: Chaetomium cochliodes CH1-V10, Mucor pseudolusitanicus MU2-T6, Thelonectria veuillotiana TH1-T3, Trichoderma atroviride TR1-T2, and Xylaria multiplex XY1-D42. These endophytes have the potential to improve in vitro propagation and facilitate ex vitro acclimatization of orchids, highlighting their importance in sustainable orchid production.

Actinobacteria isolated from less studied sites on our planet represent a huge opportunity for the discovery of novel microorganisms that may produce unique compounds with biological activity. The class actinobacteria encompasses 80% of the microbes that produce the antibacterial compounds used in medicine today. However, the resistance acquired/showed by pathogenic microorganisms opens the opportunity to explore Mexican ecosystems as a source of novel actinobacteria. Air samples have shown to be an excellent site of study, marine ecosystems which include sediments and marine organisms are important sources of novel actinobacteria and soil samples are still a promising source to isolate this microbial group. The isolation of novel actinobacteria is a dynamic strategy that depends on the expertise, patience, and talent of the techniques applied and needs to be fully explored to untap the unknown actinobacterial diversity with potential in biology.