Bacterial marginolactones trigger formation of algal gloeocapsoids, protective aggregates on the verge of multicellularity

Photosynthetic microorganisms including the green alga Chlamydomonas reinhardtii are essential to terrestrial habitats as they start the carbon cycle by conversion of CO2 to energy-rich organic carbohydrates. Terrestrial habitats are densely populated, and hence, microbial interactions mediated by natural products are inevitable. We previously discovered such an interaction between Streptomyces iranensis releasing the marginolactone azalomycin F in the presence of C. reinhardtii. Whether the alga senses and reacts to azalomycin F remained unknown. Here, we report that sublethal concentrations of azalomycin F trigger the formation of a protective multicellular structure by C. reinhardtii, which we named gloeocapsoid. Gloeocapsoids contain several cells which share multiple cell membranes and cell walls and are surrounded by a spacious matrix consisting of acidic polysaccharides. After azalomycin F removal, gloeocapsoid aggregates readily disassemble, and single cells are released. The presence of marginolactone biosynthesis gene clusters in numerous streptomycetes, their ubiquity in soil, and our observation that other marginolactones such as desertomycin A and monazomycin also trigger the formation of gloeocapsoids suggests a cross-kingdom competition with ecological relevance. Furthermore, gloeocapsoids allow for the survival of C. reinhardtii at alkaline pH and otherwise lethal concentrations of azalomycin F. Their structure and polysaccharide matrix may be ancestral to the complex mucilage formed by multicellular members of the Chlamydomonadales such as Eudorina and Volvox. Our finding suggests that multicellularity may have evolved to endure the presence of harmful competing bacteria. Additionally, it underlines the importance of natural products as microbial cues, which initiate interesting ecological scenarios of attack and counter defense.

Staphylococcus aureus Floating Biofilm Formation and Phenotype in Synovial Fluid Depends on Albumin, Fibrinogen, and Hyaluronic Acid

Biofilms are typically studied in bacterial media that allow the study of important properties such as bacterial growth. However, the results obtained in such media cannot take into account the bacterial localization/clustering caused by bacteria–protein interactions in vivo and the accompanying alterations in phenotype, virulence factor production, and ultimately antibiotic tolerance. We and others have reported that methicillin-resistant or methicillin-susceptible Staphylococcus aureus (MRSA or MSSA, respectively) and other pathogens assemble a proteinaceous matrix in synovial fluid. This proteinaceous bacterial aggregate is coated by a polysaccharide matrix as is characteristic of biofilms. In this study, we identify proteins important for this aggregation and determine the concentration ranges of these proteins that can reproduce bacterial aggregation. We then test this protein combination for its ability to cause marked aggregation, antibacterial tolerance, preservation of morphology, and expression of the phenol-soluble modulin (PSM) virulence factors. In the process, we create a viscous fluid that models bacterial behavior in synovial fluid. We suggest that our findings and, by extension, use of this fluid can help to better model bacterial behavior of new antimicrobial therapies, as well as serve as a starting point to study host protein–bacteria interactions characteristic of physiological fluids.

Functional Properties of Kefiran in Medical field and food industry

: Kefir is produced through the fermentation of milk using kefir grain as a starter culture. Kefir grains include heterogeneous microorganisms embedded in a polysaccharide matrix called kefiran which is considered a biofilm, it also has many uses due to its therapeutic values. Kefiran is a microbial exopolysaccharide (EPS) obtained from the flora (acid- lactic bacteria and yeasts) of kefir grains and glucose units, in almost the same proportion. Kefiran has prebiotic nature agitating the growth of probiotics in the gastrointestinal tract of the human entity. It extends certain therapeutic benefits through balancing the microbiota in the intestine. This review presents the most recent advances regarding kefir and kefiran, their cultural condition, biological activities, and potential applications in the health and food industries.

Uranium immobilization at microbial biofilms on upper water horizons loams nearby sludge repository

<p>Sludge and slurry uranium repositories of ore processing wastes built in the middle of the 20th century lost their waterproofing properties over time, which leads to the upper aquifers pollution with uranium, heavy metals, sludge macrocomponents: anions of nitrates, sulfates, carbonates, calcium and iron. It is known that the uranium behavior in the environment depends on its oxidation-reduction potential, which determines its oxidation state and solubility. High nitrate content in aquatic systems leads to the uranium migration in the highly oxidized form and minimizes its sorption on the rocks minerals. </p><p>Biogenic elements solution in waters can lead to the microbiota activity stimulation and biogeochemical uranium immobilization. Nitrate consumption leads to the redox potential decreasing and uranium reduction to insoluble forms. It is known that the most stable form of microorganisms in the environment is microbial biofilms. Their development on rock surface changes its physicochemical characteristics and sorption properties. This paper focused on changing the physicochemical and mineralogical parameters of rocks after microbial growth and its effect on the uranium immobilization. It should be noted that in situ bioremediation is one of the promising and inexpensive methods of groundwater remediation. Therefore, an assessment of the role of microbial biofilms in the immobilization of uranium will provide important information for predicting the effectiveness of the bioremediation.  </p><p>Angarsk Electrochemical Combine AECC (Irkutsk Region, Russia) is engaged in the processing of uranium ores and concentrates; has sludge storage facilities on the territory, which for a long time have contaminated the upper aquifers with nitrate ions, ammonium, uranium and other components. The main minerals of upper aquatic horizons weathered sandstone are: quartz, plagioclase, K-feldspar, kaolinite, smectite, specular stone, illite-smectite, vermiculite, chlorite, amphibole and apatite in trace amounts. The clay component is more than 20% with a kaolinite predomination. </p><p>In laboratory experiments, the modeling of the growth of microbial biofilms on rocks from contaminated and uncontaminated areas of the formation was carried out by adding organic substrates. Samples were dominated by representatives of the family <em>Pseudomonadaceae</em>, known for their ability to form biofilms and wide range of metabolic capabilities. An uneven distribution of biofilm on the sand was established, presumably in areas containing an increase in the amount of biogenic elements - Ca, Fe, etc., as well as organic carbon. On average, after 15 days, the coverage area of the polysaccharide matrix was 20-30%. The appearance of a polysaccharide matrix can lead to a change in the sorption capacity of rocks and to formation of local zones of uranium accumulation in organic matter. </p><p>As a result of microbial action, the dissolution of carbonate minerals and a number of changes in the composition of clay sandstones is noted. The microbial effect on rocks leads to a multidirectional change in their sorption capacity in relation to uranium. The formation of an exopolysaccharide matrix increases the sorption capacity of rocks due to the appearance of new functional groups. Moreover, with strong microbial fouling, it can lead to a decrease in uranium sorption.</p><p>This work was supported by a grant from RFBR 20-05-00602 A.</p>

The Extracellular Polysaccharide Matrix of Pseudomonas aeruginosa Biofilms Is a Determinant of Polymorphonuclear Leukocyte Responses

ABSTRACTBacterial biofilms may cause chronic infections due to their ability to evade clearance by the immune system and antibiotics. The persistent biofilms induce a hyperinflammatory state that damages the surrounding host tissue. Knowledge about the components of biofilms that are responsible for provoking the harmful but inefficient immune response is limited. Flagella are known to stimulate the response of polymorphonuclear leukocytes (PMNs) to planktonic solitary bacteria. However, we provide evidence that flagella are not a prerequisite for the response of PMNs to Pseudomonas aeruginosa biofilms. Instead, we found that extracellular matrix polysaccharides in P. aeruginosa biofilms play a role in the response of PMNs toward biofilms. Using a set of P. aeruginosa mutants with the ability to produce a subset of matrix exopolysaccharides, we found that P. aeruginosa biofilms with distinct exopolysaccharide matrix components elicit distinct PMN responses. In particular, the PMNs respond aggressively toward a biofilm matrix consisting of both Psl and alginate exopolysaccharides. These findings are relevant for therapeutic strategies aimed at dampening the collateral damage associated with biofilm-based infections.

Living the Sweet Life: How Liquorilactobacillus hordei TMW 1.1822 Changes Its Behavior in the Presence of Sucrose in Comparison to Glucose

Liquorilactobacillus (L.) hordei (formerly Lactobacillus hordei) is one of the dominating lactic acid bacteria within the water kefir consortium, being highly adapted to survive in this environment, while producing high molecular weight dextrans from sucrose. In this work, we extensively studied the physiological response of L. hordei TMW 1.1822 to sucrose compared to glucose, applying label-free, quantitative proteomics of cell lysates and exoproteomes. This revealed the differential expression of 53 proteins within cellular proteomes, mostly associated with carbohydrate uptake and metabolism. Supported by growth experiments, this suggests that L. hordei TMW 1.1822 favors fructose over other sugars. The dextransucrase was expressed irrespectively of the present carbon source, while it was significantly more released in the presence of sucrose (log2FC = 3.09), being among the most abundant proteins within exoproteomes of sucrose-treated cells. Still, L. hordei TMW 1.1822 expressed other sucrose active enzymes, predictively competing with the dextransucrase reaction. While osmolysis appeared to be unlikely, sucrose led to increased release of a multitude of cytoplasmic proteins, suggesting that biofilm formation in L. hordei is not only composed of a polysaccharide matrix but is also of proteinaceous nature. Therefore, our study highlights the intrinsic adaptation of water kefir-borne L. hordei to sucrose-rich habitats and provides fundamental knowledge for its use as a starter culture in plant-based food fermentations with in situ dextran formation.

An inkjet-printed polysaccharide matrix for on-chip sample preparation in point-of-care cell counting chambers

Gellan/trehalose layers were tailored to optimize on-chip storage and release of antibodies in a simple point-of-care CD4 counting chip with excellent agreement with standard methods.