An adhesion-promoting protein involved in the binding of Lactobacillus fermentum strain 104R to small intestinal mucus from piglets and to partially purified gastric mucin was isolated and characterized. Spent culture supernatant fluid and bacterial cell wall extracts were fractionated by ammonium sulfate precipitation and gel filtration. The active fraction was purified by affinity chromatography. The adhesion-promoting protein was detected in the fractions by adhesion inhibition and dot blot assays and visualized by polyacrylamide gel electrophoresis (PAGE), sodium dodecyl sulfate-PAGE, and Western blotting with horseradish peroxidase-labeled mucus and mucin. The active fraction was characterized by estimating the relative molecular weight and by assessing the presence of carbohydrates in, and heat sensitivity of, the active region of the adhesion-promoting protein. The purified protein was digested with porcine trypsin, and the peptides were purified in a SMART system. The peptides were tested for adhesion to horseradish peroxidase-labeled mucin by using the dot blot adhesion assay. Peptides which bound mucin were sequenced. It was shown that the purified adhesion-promoting protein on the cell surface of L. fermentum 104R is extractable with 1 M LiCl and low concentrations of lysozyme but not with 0.2 M glycine. The protein could be released to the culture supernatant fluid after 24 h of growth and had affinity for both small intestinal mucus and gastric mucin. In the native state this protein was variable in size, and it had a molecular mass of 29 kDa when denatured. The denatured protein did not contain carbohydrate moieties and was not heat sensitive. Alignment of amino acids of the adhering peptides with sequences deposited in the EMBL data library showed poor homology with previously published sequences. The protein represents an important molecule for development of probiotics.

Knowledge regarding the diversity of methanogenic archaeal communities in hypersaline environments is limited because of the lack of efficient cultivation efforts as well as their low abundance and metabolic activities. In this study, we explored the microbial communities in hypersaline microbial mats. Bioinformatic analyses showed significant differences among the archaeal community structures for each studied site. Taxonomic assignment based on 16S rRNA and methyl coenzyme-M reductase (mcrA) gene sequences, as well as metagenomic analysis, corroborated the presence of Methanosarcinales. Furthermore, this study also provided evidence for the presence of Methanobacteriales, Methanomicrobiales, Methanomassiliicoccales, Candidatus Methanofastidiosales, Methanocellales, Methanococcales and Methanopyrales, although some of these were found in extremely low relative abundances. Several mcrA environmental sequences were significantly different from those previously reported and did not match with any known methanogenic archaea, suggesting the presence of specific environmental clusters of methanogenic archaea in Guerrero Negro. Based on functional inference and the detection of specific genes in the metagenome, we hypothesised that all four methanogenic pathways were able to occur in these environments. This study allowed the detection of extremely low-abundance methanogenic archaea, which were highly diverse and with unknown physiology, evidencing the presence of all methanogenic metabolic pathways rather than the sheer existence of exclusively methylotrophic methanogenic archaea in hypersaline environments.

Microalgae offer distinct advantages as a nutritional source for aquaculture and as a means of wastewater bioremediation. Studying the phycosphere bacteria and understanding their complex interactions is essential to optimizing high-quality biomass growth. This study aimed to isolate, characterize, and identify bacteria from the phycosphere of marine microalgae and to determine their potential to enhance growth, metabolism, and bioremediation capabilities of Chaetoceros calcitrans in stress nutrient-poor media simulating aquaculture wastewater enriched with nitrate, nitrite, or phosphorus. Bacterial characterization included tests for auxin and siderophore production, biofilm formation, amylase activity, phosphate solubilization, mobility, and antagonism evaluation. When Alteromonas macleodii, Bacillus cereus, and Marinobacter sp. were selected and then enriched (10⁷ CFU/mL) in co-culture with C. calcitrans, growth levels significantly increased in four of six Synthetic Aquaculture Wastewater (SAW) media. Pigment levels were higher in five of six SAW media, and lipid levels were higher in SAW rich in nitrite (SAWni50) and phosphorus (SAWpho50). In addition, C. calcitrans with or without the bacterial consortium demonstrated excellent phosphorus bioremediation, achieving 67.6% average removal in SAWpho50. Nitrate and nitrite assimilation rates were approximately 10% in SAWna and SAWni50. This study marks the inaugural identification of these bacteria as microalga growth-promoting bacteria (MGPB) for enhancing growth and lipid and pigment production in C. calcitrans, and it also documents a maximum of 69.13% phosphorus removal.

One of the main problems in laboratories of oyster seed production occurs in the stage of settlement or fixation and metamorphosis of the larvae. The organisms develop drastic morphological and physiological changes at this stage, exposing them to attack by pathogenic microorganisms. Numerous studies indicate that before larval settlement to a substrate, they require bacteria to stimulate and induce the process. In this study, Japanese oyster (Crassostrea gigas) larvae were fed with combinations of microalgae and bacteria previously selected for their probiotic potential; their impact on survival, growth, and settlement was evaluated. Larvae D of 12 days old were provided by a private company and transported to the laboratory under controlled conditions. Probiotic bacteria Lactobacillus plantarum 69Cr, L. fermentum 101Cc, and L. casei 43Cg were reactivated on MRS and applied at a concentration of 1×104 CFU mL-1. Microalgae Isochrysis galbana and Chaetoceros calcitrans were grown in F2 medium and supplied at a concentration of 3×104 cells mL-1. Results showed, in all treatments, a survival range of 39-53%, growth of 300-310 μm, and 34-56.5% settlement. However, the best bacteria combined with I. galbana and C. calcitrans was L. plantarum 69Cr with a 54% survival, 310 μm growth, and 56.5% settlement. It is concluded that the combination of L. plantarum 69Cr with I. galbana and C. calcitrans has the potential to be used in the production of Japanese oyster larvae.