Diversity of culturable yeasts associated with zoanthids from Brazilian reef and its relation with anthropogenic disturbance

Spatio-temporal distribution and biotechnological potential of culturable yeasts in the intertidal sediments and seawater of Aoshan Bay, China

Marine yeasts play a crucial role in marine microbial ecology, facilitating the biogeochemical cycling of carbon and nitrogen in marine ecosystems, while also serving as important reservoirs of bioactive compounds with extensive applications in pharmaceuticals, agriculture, and various industries. Intertidal flats, characterized by their complex ecological dynamics, are postulated to harbor a wealth of yeast resources. This study employed a culture-dependent approach to assess the diversity, spatio-temporal distribution, and biotechnological potential of yeast communities residing within the intertidal sediments and seawater of Aoshan Bay. A total of 392 yeast strains were identified from 20 distinct genera, encompassing 43 recognized species and four candidate novel species. Notably, 17 of these species were identified as novel occurrences in marine environments, underscoring the rich yeast biodiversity of the Aoshan Bay ecosystem, with Candida emerging as the dominant genus in both sedimentary and aqueous habitats. Yeast community composition exhibited significant spatial and temporal variation, with peak diversity and abundance observed in autumn, the subtidal zone, and the surface soil layer. No clear pattern, however, emerged linking these shifts to specific changes in community composition, highlighting the complex interactions between microbial communities, environmental variables, and anthropogenic disturbance. Although several yeast species isolated here have been previously recognized for their biotechnological potential, their diverse and abundant extracellular enzyme profiles were characterized, further highlighting their crucial role in organic matter decomposition and nutrient cycling within the tidal ecosystem, as well as their potential applicability in the food, fine chemical, textile, and pharmaceutical industries.IMPORTANCEThis study presents groundbreaking insights into the yeast diversity of Aoshan Bay, offering invaluable information on their spatial and temporal distribution patterns, as well as their biotechnological potential in the tidal environment. The findings reveal that the eutrophic intertidal flat is a rich repository of yeasts with abundant extracellular enzymatic activity and an important role in nutrient cycling and decomposition processes. Also, these yeasts serve as crucial indicators of ecosystem health and function and are excellent candidates for biotechnological and industrial applications. Collectively, this study not only expands our knowledge of the diversity and distribution of intertidal yeasts but also highlights their promising potential for biotechnological applications.

Brazilian mangrove sediments as a source of biosurfactant-producing yeast Pichia pseudolambica for bioremediation

This work highlights the biosurfactant production potential of yeasts from mangroves in northeastern Brazil. The biosurfactants were evaluated by their emulsifying capacity (EI24), with 6 isolates showing values between 50% and 62%. Surfactant properties from crude extract were measured using drop collapse, oil displacement, Parafilm® M, surface tension and critical micellar concentration tests. The effects of temperature, salinity, pH, and the ability to emulsify different hydrocarbons were analyzed, showing a promising potential of the yeast species investigated to tolerance to high temperatures and acidic pH, in addition to emulsifying different sources of hydrocarbons with environmental impact. It is important to note that the Pichia pseudolambica isolates showed a remarkable ability to reduce the surface tension of water, from 70.82 mN/m to 36.47 mN/m. In addition, the critical micellar concentration (CMC) values ranged from 7 to 16 mg/mL, highlighting the promising surfactant activity of these isolates for future applications. It was identified that the biosurfactant adhered to the yeast cell wall, and FTIR and 1H NMR spectroscopy analysis was carried out on the yeast biomass and its post-sonication supernatant. The results indicate the presence of characteristic functional groups and peaks found in biosurfactants of a glycolipid nature. Taking together the results reveals the promising potential of biosurfactant biosynthesis of P. pseudolambica yeast, a trait not reported in the literature so far for this species. P. pseudolambica presents a relevant metabolic potential for alternative substrate use and resilience to adverse conditions that could enable it to produce biosurfactants for the biotechnological remediation of areas contaminated by oil derivatives. The metabolic properties herein investigated, together with their presence in Brazilian mangroves, make P. pseudolambica an emerging candidate for developing industrial processes and sustainable strategies for the recovery of ecosystems impacted by oil spills, being positioned as a sustainable alternative to conventional surfactants.

Pichia kudriavzevii as feed additive in Nile tilapia (Oreochromis niloticus) diet

Yeasts are unicellular eukaryotic microorganisms extensively employed in various applications, notably as an alternative source of protein in feeds, owing to their nutritional benefits. Despite their potential, marine and mangrove yeast species used in the aquaculture industry have received little attention in the Philippines. Pichia kudriavzevii (A2B R1 ISO 3), sourced from bark samples, was selected and mass-produced due to its high protein content and amino acid profile. The dried biomass of P. kudriavzevii was incorporated into the diets of Nile tilapia (Oreochromis niloticus) juveniles at varying inclusion levels (0, 1, 2, and 4 g/kg diet) and its effect on their growth performance, body composition, and liver and intestinal morphology was assessed after 40 days of feeding. The groups that received P. kudriavzevii at a concentration of 2 g/kg diet exhibited higher final body weight, percent weight gain, and specific growth rate in comparison to the other treatment groups. Whole body proximate composition did not vary among the dietary groups. Intestinal and liver histopathology also indicated no abnormalities. These findings suggest the potential of ascomycetous P. kudriavzevii as a beneficial feed additive in Nile tilapia diets, warranting further investigation into its long-term effects and broader applications in fish culture.

Biosurfactants production by marine yeasts isolated from zoanthids and characterization of an emulsifier produced by Yarrowia lipolytica LMS 24B

The present study investigates the potential for biosurfactant production of 19 marine yeast species obtained from zoanthids. Using the emulsification index test to screen the samples produced by the marine yeasts, we verified that five isolates exhibited an emulsification index ≥50%. Additional tests were performed on such isolates, including oil displacement, drop collapse, Parafilm M assay, and surface tension measurement. The tolerance of produced biosurfactants for environmental conditions was also analyzed, especially considering the media's temperature, pH, and salinity. Moreover, the surfactant's ability to emulsify different hydrocarbon sources and to metabolize kerosene as the sole carbon source was evaluated in vitro. Our results demonstrate that yeast biosurfactants can emulsify hydrocarbon sources under different physicochemical conditions and metabolize kerosene as a carbon source. Considering the Yarrowia lipolytica LMS 24B as the yeast model for biosurfactant production from the cell's wall biomass, emulsification indexes of 61.2% were obtained, even at a high temperature of 120 °C. Furthermore, the Fourier-transform middle infrared spectroscopy (FTIR) analysis of the biosurfactant's chemical composition revealed the presence of distinct functional groups assigned to a glycoprotein complex. Considering the status of developing new bioproducts and bioprocesses nowadays, our findings bring a new perspective to biosurfactant production by marine yeasts, especially Y. lipolytica LMS 24B. In particular, the presented results validate the relevance of marine environments as valuable sources of genetic resources, i.e., yeast strains capable of metabolizing and emulsifying petroleum derivatives.

Tremella ananatis sp. nov. and Tremella lamprococci sp. nov., two yeast species associated with bromeliads

Eight yeast isolates with an affinity to the genus Tremella were obtained from bromeliads from different locations in Brazil. Although the formation of basidia and basidiocarp were not observed, on the basis of the results of sequence analysis of the D1/D2 domain of the large subunit (LSU) rRNA gene and internal transcribed spacer (ITS) region, we suggest that these isolates represent two novel species of the genus Tremella. These yeasts are phylogenetically related to Tremella saccharicola and Tremella globispora. Therefore, we propose Tremella ananatis sp. nov. and Tremella lamprococci sp. nov. as novel yeast species of the order Tremellales (Agaricomycotina, Basidiomycota). Sequence analysis revealed that Tremella ananatis sp. nov. differs by 11 and 28 nucleotide substitutions from Tremella saccharicola in the D1/D2 sequence and ITS region, respectively. Moreover, Tremella lamprococci sp. nov. differs by 15 and 29 nucleotide substitutions from Tremella globispora in the D1/D2 sequence and ITS region, respectively. The holotypes of Tremella ananatis sp. nov. and Tremella lamprococci sp. nov. are CBS 14568T and CBS 14567T, and the MycoBank numbers are MB840480 and MB840481, respectively.

Wickerhamiella martinezcruziae f. a., sp. nov., a yeast species isolated from tropical habitats

Four yeast isolates with an affinity to the genus Wickerhamiella were obtained from beach sand, a marine zoanthid and a tree exudate at different localities in Brazil. Two other isolates with almost identical ITS and D1/D2 sequences of the large subunit rRNA gene were isolated from the small intestine of cattle and a grease trap in Thailand. These isolates represent a novel species phylogenetically related to Wickerhamiella verensis, Wickerhamiella osmotolerans, Wickerhamiella tropicalis, Wickerhamiella sorbophila and Wickerhamiella infanticola. The novel species differs by 15-30 nucleotide differences from these species in the D1/D2 sequences. The name Wickerhamiella martinezcruziae f.a., sp. nov. is proposed. The holotype of Wickerhamiella martinezcruziae sp. nov. is CBS 16104^T. The MycoBank number is MB 839328.

Cultivable yeasts associated with marine sponges in the Gulf of Thailand, South China Sea

Marine sponges harbor numerous microorganisms, among which sponge-associated yeasts are the least explored. To gain greater knowledge of sponge-associated yeasts, an investigation was therefore performed on marine sponges in Sattahip Bay, Gulf of Thailand, South China Sea. Seventy-one (71) marine sponge samples were collected at sites near Samae-san, Mu, and Khram islands, and were subsequently identified as 17 sponge species in 14 genera. Eighty-seven (87) yeast strains were isolated from 42 samples. The identification of yeasts by similarity analysis of the D1/D2 domain sequences of the large subunit rRNA gene revealed that 64% of the yeast strains obtained belonged to the phylum Basidiomycota, while the remaining strains belonged to the phylum Ascomycota. The strains that belonged to Ascomycota comprised 11 known yeast species in five genera (Candida, Kodamaea, Magnusiomyces, Meyerozyma, and Pichia). The strains belonging to the phylum Basidiomycota comprised 14 known yeast species in eight genera (Cutaneotrichosporon, Cystobasidium, Naganishia, Papiliotrema, Rhodosporidiobolus, Rhodotorula, Trichosporon, and Vishniacozyma). In addition, three strains represented a potential novel species closest to Cys. slooffiae; one strain represented a potential novel species closest to R. toruloides; and one strain represented a potential novel species closest to V. foliicola. The species with the highest occurrence was Rhodotorula mucilaginosa. No marked difference was found in the principal coordinates analysis of the ordinations of yeast communities from the three sampling sites. The estimation using EstimateS software showed that the expected species richness was higher than the observed species richness. As the marine sponge-yeast association remains unclear, more systematic investigations should be carried out.

Assessment of Diversity of Culturable Marine Yeasts Associated with Corals and Zoanthids in the Gulf of Thailand, South China Sea

Marine yeasts can occur in a wide range of habitats, including in marine invertebrates, in which they may play important roles; however, investigation of marine yeasts in marine invertebrates is scarce. Therefore, this study aims to explore the diversity of yeasts associated with corals and zoanthids in the Gulf of Thailand. Thirty-three coral and seven zoanthid samples were collected at two sampling sites near Mu and Khram islands. Fifty yeast strains were able to be isolated from 25 of the 40 samples collected. Identification based on sequence analyses of the D1/D2 domain of the large subunit rRNA gene revealed a higher number of strains in the phylum Basidiomycota (68%) than in the phylum Ascomycota. The ascomycetous yeasts comprised nine known species from four genera (Candida, Meyerozyma, Kodamaea, and Wickerhamomyces), whereas the basidiomycetous yeasts comprised 10 known species from eight genera (Vishniacozyma, Filobasidium, Naganishia, Papiliotrema, Sterigmatomyces, Cystobasidium, Rhodotorula, and Rhodosporidiobolus) and one potentially new species. The species with the highest occurrence was Rhodotorula mucilaginosa. Using principal coordinate analysis (PCoA) ordination, no marked differences were found in the yeast communities from the two sampling sites. The estimation of the expected richness of species was higher than the actual richness of species observed.

Diversity of filamentous fungi associated with coral and sponges in coastal reefs of northeast Brazil

Fungi are known to form associations with various marine organisms and substrata such as sponges and corals, both as potential symbionts or pathogens. These microorganisms occupy an ecological niche that has recently attracted great attention due to their potential in either ecological or pharmaceutical advances. However, the interaction between marine invertebrates and fungi is still poorly understood, including how they are affected by anthropogenic actions. Here, we identified 89 fungal isolates through sequencing of the ITS rDNA region obtained from the various sponge and coral species collected at two northeast Brazilian reefs. We found 43 species of fungi from 16 genera, all belonging to phylum Ascomycota. The sponges and coral shared four genera: Aspergillus, Penicillium, Trichoderma, and Cladosporium, all commonly found in terrestrial habitats and associated with marine invertebrates. We observed some unusual species in relation to the marine environment, such as Clonostachys rosea and Neopestalotiopsis clavispora, most of them related to plants, either as saprophytic or pathogenic, suggesting that these species were transported from the surrounding terrestrial environment to the reefs. In addition, some isolates represent possible undescribed species, reinforcing the importance of studying the marine environment in relation to its ecological and biotechnological importance.