Fungi in mangrove ecosystems and their potential applications

Chemical Constituents and Biological Activities of Bruguiera Genus and Its Endophytes: A Review

The genus Bruguiera, a member of the Rhizophoraceae family, is predominantly found in coastal areas as a mangrove plant, boasting a rich and diverse community of endophytes. This review systematically compiled approximately 496 compounds derived from both the Bruguiera genus and its associated endophytes, including 152 terpenoids, 17 steroids, 16 sulfides, 44 alkaloids and peptides, 66 quinones, 68 polyketides, 19 flavonoids, 38 phenylpropanoids, 54 aromatic compounds, and 22 other compounds. Among these, 201 compounds exhibited a spectrum of activities, including cytotoxicity, antimicrobial, antioxidant, anti-inflammatory, antiviral, antidiabetic, insecticidal and mosquito repellent, and enzyme inhibitory properties, etc. These findings provided promising lead compounds for drug discovery. Certain similar or identical compounds were found to be simultaneously present in both Bruguiera plants and their endophytes, and the phenomenon of their interaction relationship was discussed.

Diversity of fungal endophytes from mangrove plants of Santa Catarina Island, Brazil

The mangrove ecosystem plays a crucial role in preserving the biodiversity of plants, animals, and microorganisms that are essential for materials cycles. However, the exploration of endophytic fungi isolated from mangroves, particulary in Santa Catarina (SC, Brazil), remains limited. Therefore, the purpose of this study was to assess the biodiversity of endophytic fungi found in Avicennia schaueriana, Laguncularia racemosa, Rhizophora mangle, and Spartina alterniflora from two mangroves on the Island of Santa Catarina: one impacted by anthropic action (Itacorubi mangrove) and the other environmentally preserved (Ratones mangrove). Samplings were carried out between January 2020 and May 2021. Fungi were isolated from leaves, stems, and roots, identified, and clustered into groups through morphological characteristics. Further, a representative strain of each group was identified through ITS1 sequencing. A total of 373 isolates were obtained from plant tissues, of which 96 and 277 isolates were obtained from Itacorubi and Ratones mangroves, respectively. Molecular identification showed that the endophytic fungal community comprised at least 19 genera. The data on fungal community diversity revealed comparable diversity indices for genera in both mangroves. However, we observed differences in the total frequency of fungal genera between impacted (27.38%) and non-impacted (72.62%) mangroves. These findings suggest that anthropic activities in and around the Santa Catarina mangroves have had negative impact on the frequency of endophytic fungi. This emphasizes the reinforcing the significance of preserving these environments to ensure the maintenance of fungal community diversity.

Mushrooms Adapted to Seawater: Two New Species of Candolleomyces (Basidiomycota, Agaricales) from China

Marine fungi have been studied for a long history in many realms, but there are few reports on marine mushrooms. In this study, marine fungi with conspicuous subglobose sequestrate basidioma were discovered from mangrove forests in South China. They grow on the deadwood of mangroves in the intertidal zone, periodically submerging into seawater due to the tide. Some marine animals were observed to nest in their basidiomata or consume them as food. The pileus-gleba-inner veil complex (PGI) of the basidioma was observed to be detached from the stipe and transferred into seawater by external forces, and drifting on sea to spread spores after maturity. The detachment mechanism of their PGIs was revealed through detailed microscopic observations. The contrast culturing experiment using freshwater and seawater potato dextrose agar media showed they have probably obligately adapted to the marine environment. Based on morphological and molecular phylogenetic evidence, two new species of Candolleomyces (Basidiomycota, Agaricales), namely C. brunneovagabundus and C. albovagabundus, were described. They are similar and close to each other, but can be distinguished by the size and color of the basidioma, and the size of the basidiospores.

Dechlorination of wastewater from shell-based glucosamine processing by mangrove wetland-derived fungi

Wastewater from processing crustacean shell features ultrahigh chloride content. Bioremediation of the wastewater is challenging due to the high chloride ion content, making it inhospitable for most microorganisms to survive and growth. In this study, mangrove wetland-derived fungi were first tested for their salt tolerance, and the highly tolerant isolates were cultured in shrimp processing wastewater and the chloride concentration was monitored. Notably, the filamentous fungal species Aspergillus piperis could remove over 70% of the chloride in the wastewater within 3 days, with the fastest biomass increase (2.01 times heavier) and chloride removal occurring between day one and two. The chloride ions were sequestered into the fungal cells. The genome of this fungal species contained Cl- conversion enzymes, which may have contributed to the ion removal. The fungal strain was found to be of low virulence in larval models and could serve as a starting point for further considerations in bioremediation of shell processing wastewater, promoting the development of green technology in the shell processing industry.

Novel chromosomes and genomes provide new insights into evolution and adaptation of the whole genome duplicated yeast-like fungus TN3-1 isolated from natural honey

Aureobasidium melanogenum TN3-1 strain and A. melanogenum P16 strain were isolated from the natural honey and the mangrove ecosystem, respectively. The former can produce much higher pullulan from high concentration of glucose than the latter. In order to know what happened to their genomes, the PacBio sequencing and Hi-C technologies were used to create the first high-quality chromosome-level reference genome assembly of A. melanogenum TN3-1 (51.61 Mb) and A. melanogenum P16 (25.82 Mb) with the contig N50 of 2.19 Mb and 2.26 Mb, respectively. Based on the Hi-C results, a total of 93.33% contigs in the TN3-1 strain and 92.31% contigs in the P16 strain were anchored onto 24 and 12 haploid chromosomes, respectively. The genomes of the TN3-1 strain had two subgenomes A and B. Synteny analysis showed that the genomic contents of the two subgenomes were asymmetric with many structural variations. Intriguingly, the TN3-1 strain was revealed as a recent hybrid/fusion between the ancestor of A. melanogenum CBS105.22/CBS110374 and the ancestor of another unidentified strain of A. melanogenum similar to P16 strain. We estimated that the two ancient progenitors diverged around 18.38 Mya and merged around 10.66-9.98 Mya. It was found that in the TN3-1 strain, telomeres of each chromosome contained high level of long interspersed nuclear elements (LINEs), but had low level of the telomerase encoding gene. Meanwhile, there were high level of transposable elements (TEs) inserted in the chromosomes of the TN3-1 strain. In addition, the positively selected genes of the TN3-1 strain were mainly enriched in the metabolic processes related to harsh environmental adaptability. Most of the stress-related genes were found to be related to the adjacent LTRs, and the glucose derepression was caused by the mutation of the Glc7-2 in the Snf-Mig1 system. All of these could contribute to its genetic instability, genome evolution, high stress resistance, and high pullulan production from glucose.

Anti-Tumor Secondary Metabolites Originating from Fungi in the South China Sea's Mangrove Ecosystem

A mangrove is a unique ecosystem with abundant resources, in which fungi are an indispensable microbial part. Numerous mangrove fungi-derived secondary metabolites are considerable sources of novel bioactive substances, such as polyketides, terpenoids, alkaloids, peptides, etc., which arouse people's interest in the search for potential natural anti-tumor drugs. This review includes a total of 44 research publications that described 110 secondary metabolites that were all shown to be anti-tumor from 39 mangrove fungal strains belonging to 18 genera that were acquired from the South China Sea between 2016 and 2022. To identify more potential medications for clinical tumor therapy, their sources, unique structures, and cytotoxicity qualities were compiled. This review could serve as a crucial resource for the research status of mangrove fungal-derived natural products deserving of further development.

Temperature drives the assembly of Bacillus community in mangrove ecosystem

Mangroves are located at the interface of terrestrial and marine environments, and experience fluctuating conditions, creating a need to better explore the relative role of the bacterial community. Bacillus has been reported to be the dominant group in the mangrove ecosystem and plays a key role in maintaining the biodiversity and function of the mangrove ecosystem. However, studies on bacterial and Bacillus community across four seasons in the mangrove ecosystem are scarce. Here, we employed seasonal large-scale sediment samples collected from the mangrove ecosystem in southeastern China and utilized 16S rRNA gene amplicon sequencing to reveal bacterial and Bacillus community structure changes across seasons. Compared with the whole bacterial community, we found that Bacillus community was greatly affected by season (temperature) rather than site. The key factors, NO₃-N and NH₄-N showed opposite interaction with superabundant taxa Bacillus taxa (SAT) and three rare Bacillus taxa including high rare taxa (HRT), moderate rare taxa (MRT) and low rare taxa (LRT). Network analysis suggested the co-occurrence of Bacillus community and Bacillus-bacteria, and revealed SAT had closer relationship compared with rare Bacillus taxa. HRT might act crucial response during the temperature decreasing process across seasons. This study fills a gap in addressing the assembly of Bacillus community and their role in maintaining microbial diversity and function in mangrove ecosystem.

Polycyclic aromatic hydrocarbons (PAHs) in mangrove ecosystems: A review

Polycyclic aromatic hydrocarbons (PAHs) are organic pollutants of increasing concern in the different fields of the environment and human health. There are 16 of them that are recognized as priority pollutants by the US environmental protection agency due to their mutagenic and carcinogenic potentials. Due to their hydrophobicity and stability, they are persistent in the environment and can be transported over long distances. Their toxicological effects on multiple species, including humans, as well as their bioaccumulation in the food web became major topics in organic pollutants research this last decade. In the environment, multiple studies have been conducted on their accumulation in the soil and their degradation processes resulting in numerous review papers. However, the dynamics of PAHs in mangrove ecosystems is not yet completely understood. In this review paper, an exhaustive presentation of what is known about PAHs and their transfer, accumulation, and degradation in mangrove ecosystems is offered. This article brings to light the knowledge already acquired on the subject and the perspective research necessary to fully comprehend PAHs dynamics in mangrove ecosystems.

Cave Microbes as a Potential Source of Drugs Development in the Modern Era

The world is constantly facing threats, including the emergence of new pathogens and antibiotic resistance among extant pathogens, which is a matter of concern. Therefore, the need for natural and effective sources of drugs is inevitable. The ancient and pristine ecosystems of caves contain a unique microbial world and could provide a possible source of antimicrobial metabolites. The association between humans and caves is as old as human history itself. Historically, cave environments have been used to treat patients with respiratory tract infections, which is referred to as speleotherapy. Today, the pristine environment of caves that comprise a poorly explored microbial world is a potential source of antimicrobial and anticancer drugs. Oligotrophic conditions in caves enhance the competition among microbial communities, and unique antimicrobial agents may be used in this competition. This review suggests that the world needs a novel and effective source of drug discovery. Therefore, being the emerging spot of modern human civilization, caves could play a crucial role in the current medical crisis, and cave microorganisms may have the potential to produce novel antimicrobial and anticancer drugs.

Protection of Halophytes and Their Uses for Cultivation of Saline-Alkali Soil in China

Over 800 million hectares of arable lands are affected by salinity in the world. In China, saline-alkali soils account for 25% of farmland and are underutilized. One sustainable strategy to make better use of saline land is to plant halophytes, salt-tolerant plants that can survive and complete their life cycle in media containing more than 200 mM NaCl. Halophytes have potential economic value as grain, vegetable, fruit, medicine, animal feed, and biofuel feedstocks, and in greening and coastal protection. Therefore, the cultivation and protection of halophytes is very important. In the past few decades, a lot of work has been done on the protection and utilization of halophytes in saline soil improvement and development worldwide. This article focuses on the distribution of saline-alkali conditions and current measures to protect halophytes, as well as the application of halophytes in the sustainable development of saline-alkali land. This information is helpful for protection and utilization of halophytes in the sustainable development of saline land worldwide.