Bioemulsifier (BE-AM1) produced by Solibacillus silvestris AM1 is a functional amyloid that modulates bacterial cell-surface properties

Comparative negation of amphiphile production using nutrition factors: Amyloids versus biosurfactants

Microbial amphiphiles play an important role in environmental activities such as microbial signaling, bioremediation, and biofilm formation. Microorganisms rely on their unique characteristics of interfaces to carry out critical biological functions, which are helped by amphipathic biomolecules known as amphiphiles. Bacillus amyloids aid in cell adhesion and biofilm formation. Pseudomonas sp. are essential in biofilm development and are a vital survival strategy for many bacteria. Furthermore, Pseudomonas and Bacillus are well-known for their ability to produce biosurfactants with a range of applications, including bioremediation and removing biological pollutants from different environments. The study employed 31 different media types and a range of analytical techniques to assess the presence of amyloid proteins and the absence of biosurfactants in Bacillus licheniformis K125 (GQ850525.1) and Pseudomonas fluorescens CHA0. The presence of amyloid proteins was confirmed through Congo red and thioflavin T staining. The carefully constructed medium also efficiently inhibited the synthesis of biosurfactants by these bacteria. Additionally, surface tension measurements, emulsification index, thin-layer chromatography, and high-performance thin-layer chromatography analyses indicated the absence of biosurfactants in the tested media.

Importance of microbial amphiphiles: interaction potential of biosurfactants, amyloids, and other exo-polymeric-substances

Microorganisms produce a diverse group of biomolecules having amphipathic nature (amphiphiles). Microbial amphiphiles, including amyloids, bio-surfactants, and other exo-polymeric substances, play a crucial role in various biological processes and have gained significant attention recently. Although diverse in biochemical composition, these amphiphiles have been reported for common microbial traits like biofilm formation and pathogenicity due to their ability to act as surface active agents with active interfacial properties essential for microbes to grow in various niches. This enables microbes to reduce surface tension, emulsification, dispersion, and attachment at the interface. In this report, the ecological importance and biotechnological usage of important amphiphiles have been discussed. The low molecular weight amphiphiles like biosurfactants, siderophores, and peptides showing helical and antimicrobial activities have been extensively reported for their ability to work as quorum-sensing mediators. While high molecular weight amphiphiles make up amyloid fibers, exopolysaccharides, liposomes, or magnetosomes have been shown to have a significant influence in deciding microbial physiology and survival. In this report, we have discussed the functional similarities and biochemical variations of several amphipathic biomolecules produced by microbes, and the present report shows these amphiphiles showing polyphyletic and ecophysiological groups of microorganisms and hence can `be replaced in biotechnological applications depending on the compatibility of the processes.

Two Decades of Studying Functional Amyloids in Microorganisms

In the past two decades, amyloids, typically associated with human diseases, have been described to play various functional roles in nearly all life forms. The structural and functional diversity of microbial 'functional amyloids' has dramatically increased in recent years, expanding the canonical definition of these assembled molecules. Here, we provide a broad review of the current understanding of microbial functional amyloids and their diverse roles, putting the spotlight on recent discoveries in the field. We discuss their functions as structural scaffolds, surface-tension modulators, adhesion molecules, cell-cycle and gametogenesis regulators, toxins, and mediators of host-pathogen interactions. We outline how noncanonical amyloid morphologies and sophisticated regulatory mechanisms underlie their functional diversity and emphasize their therapeutic and biotechnological implications and applications.

Biological Functions of Prokaryotic Amyloids in Interspecies Interactions: Facts and Assumptions

Amyloids are fibrillar protein aggregates with an ordered spatial structure called "cross-β". While some amyloids are associated with development of approximately 50 incurable diseases of humans and animals, the others perform various crucial physiological functions. The greatest diversity of amyloids functions is identified within prokaryotic species where they, being the components of the biofilm matrix, function as adhesins, regulate the activity of toxins and virulence factors, and compose extracellular protein layers. Amyloid state is widely used by different pathogenic bacterial species in their interactions with eukaryotic organisms. These amyloids, being functional for bacteria that produce them, are associated with various bacterial infections in humans and animals. Thus, the repertoire of the disease-associated amyloids includes not only dozens of pathological amyloids of mammalian origin but also numerous microbial amyloids. Although the ability of symbiotic microorganisms to produce amyloids has recently been demonstrated, functional roles of prokaryotic amyloids in host-symbiont interactions as well as in the interspecies interactions within the prokaryotic communities remain poorly studied. Here, we summarize the current findings in the field of prokaryotic amyloids, classify different interspecies interactions where these amyloids are involved, and hypothesize about their real occurrence in nature as well as their roles in pathogenesis and symbiosis.

Functional Amyloids

When protein/peptides aggregate, they usually form the amyloid state consisting of cross β-sheet structure built by repetitively stacked β-strands forming long fibrils. Amyloids are usually associated with disease including Alzheimer's. However, amyloid has many useful features. It efficiently transforms protein from the soluble to the insoluble state in an essentially two-state process, while its repetitive structure provides high stability and a robust prion-like replication mechanism. Accordingly, amyloid is used by nature in multifaceted and ingenious ways of life, ranging from bacteria and fungi to mammals. These include (1) Structure: Templating for small chemical molecules (Pmel17), biofilm formation in bacteria (curli), assisting aerial hyphae formation in streptomycetes (chaplins) or monolayer formation at a surface (hydrophobins). (2) Reservoirs: A storage state for peptide/proteins to protect them from their surroundings or vice versa (storage of peptide hormones in mammalian secretory granules or major basic protein in eosinophils). (3) Information carriers: The fungal immune system (HET-s prion in Podospora anserina, yeast prions) or long-term memory (e.g., mnemons in yeast, cytoplasmic polyadenylation element-binding protein in aplysia). Aggregation is also used to (4) "suppress" the function of the soluble protein (e.g., Cdc19 in yeast stress granules), or (5) "signaling" through formation of oligomers (e.g., HET-s prion, necroptosis-related proteins RIP1/RIP3). This review summarizes current knowledge on functional amyloids with a focus on the amyloid systems curli in bacteria, HET-s prion in P. anserina, and peptide hormone storage in mammals together with an attempt to highlight differences between functional and disease-associated amyloids.

Amyloid protein produced by B. cereus CR4 possesses bioflocculant activity and has potential application in microalgae harvest

Bacillus cereus CR4 from the flocs of activated sludge was found to produce an extracellular bioflocculant, which was characterized as amyloid protein and demonstrated to have potential application in microalgae recovery. Cell surface amyloid production was demonstrated by fluorescence, confocal and scanning electron microscopy. Birefringence, spectral shift assay, TEM, FTIR and CD spectra confirmed the amyloid nature of the purified protein that demonstrated flocculation. The gene for amyloid protein of B. cereus CR4 was found to be related to tasA gene of amyloid protein produced by Bacillus subtilis. The results demonstrated that the amyloid protein produced by B. cereus CR4 possessed a novel bioflocculant activity which at pH below 4.5 reached to a maximum of 86.87%. The amyloid bioflocculant producing B. cereus CR4 has a potential in biotechnological application like Scenedesmus biomass recovery.

Mycelial form of dimorphic fungus Malassezia species dictates the microbial interaction

Dandruff is one of the most common clinically manifested and studied scalp disorders. It has been associated with both bacteria and fungi. Bacteria and fungi inhabiting the scalp are known to influence each other and manifestation of dandruff. Fungal and bacterial isolates from scalp epithelial flakes (dandruff) were identified by rDNA sequencing. Local oils were tested for fungal and bacterial inhibition, interaction and biofilm formation, cell-cell interactions were studied by auto aggregation and surface thermodynamics studies. The isolates Bacillus sp.C2b1 (MK036745) and Malassezia sp. C2y1 (MK036746) were inhibited by Mahabhrungraj oil. The fungal morphological switch was evident and dependent on nutrition. Cell aggregation studies suggested the interaction of bacteria with yeast (non-pathogenic) phase of the fungus. Bacterial and yeast cells were found to be compatible for biofilm formation. The fungal mycelial surfaces were found to be conducive for interaction with both bacterial cells and yeast forms. The results here indicate the significance of mycelial phase of scalp-isolated fungus in interaction with the bacterial surfaces and also with self-yeast phase surface. This is the first report of the interaction between scalp-isolated microorganisms with respect to their surface interaction capabilities.

The Contingency of Soil Microorganisms and the Selected Soil Biotic and Abiotic Parameters Under Different Land-Uses

Land use changes are local phenomena with global impact. They have an impact in a cumulative sense on biodiversity or soil degradation. This study aimed to examine the effects of different land-uses (arable land, permanent grasslands, abandoned grasslands, forest land) on the selected biotic and abiotic soil parameters in the Slovak mountain study sites Liptovská Teplička and Tajov. Biotic (microbial community structure, earthworm number and fresh body biomass, arthropod number and fresh body biomass), and abiotic chemical soil parameters (pH, total organic carbon, total nitrogen, nutrients) were measured. According to MALDI-TOF (Matrix Assisted Laser Desorption Ionization-Time of Flight), several bacterial strains were identified. Mutual relations between soil microorganisms and soil biotic and abiotic properties determined by different land uses were analysed. Microbial response expressed as average well-colour development (AWCD) values indicated relations between higher microbial diversity and higher nutrient availability at both study sites. In the comparison of land use types, permanent grasslands (PG) showed the lowest microbial activity in the depth of 0–0.1 m. But in the depth of 0.2-0.3 m in PG of both study sites, the higher microbial activity was recorded compared to the depth of 0-0.1 m. In addition, lower AWCD values in PG were in line with the lower available P and K content but higher earthworm density and biomass.

Beyond the expected: the structural and functional diversity of bacterial amyloids

Intense research has confirmed the formerly theoretical distribution of amyloids in nature, and studies on different systems have illustrated the role of these proteins in microbial adaptation and in interactions with the environment. Two lines of research are expanding our knowledge on functional amyloids: (i) structural studies providing insights into the molecular machineries responsible for the transition from monomer to fibers and (ii) studies showing the way in which these proteins might participate in the microbial fitness in natural settings. Much is known about how amyloids play a role in the social behavior of bacteria, or biofilm formation, and in the adhesion of bacteria to surfaces; however, we are still in the initial stages of understanding a complementary involvement of amyloids in bacteria-host interactions. This review will cover the following two topics: first, the key aspects of the microbial platforms dedicated to the assembly of the fibers, and second, the mechanisms by which bacteria utilize the morphological and biochemical variability of amyloids to modulate the immunological response of the host, plants and humans, contributing to (i) infection, in the case of pathogenic bacteria or (ii) promotion of the health of the host, in the case of beneficial bacteria.

Functional Amyloid and Other Protein Fibers in the Biofilm Matrix

Biofilms are ubiquitous in the natural and man-made environment. They are defined as microbes that are encapsulated in an extracellular, self-produced, biofilm matrix. Growing evidence from the genetic and biochemical analysis of single species biofilms has linked the presence of fibrous proteins to a functional biofilm matrix. Some of these fibers have been described as functional amyloid or amyloid-like fibers. Here we provide an overview of the biophysical and biological data for a wide range of protein fibers found in the biofilm matrix of Gram-positive and Gram-negative bacteria.

Microbial Investigation of Recreation Effects on Water and Soil in the Tatra National Park

Tatra National Park is considered as the most visited protected area in Slovakia. Striking a balance between the preservation of natural resources and opportunities for public recreation often forces responsible authorities to make compromises between visitation impacts and protection. In this case, the microbial investigation of recreation effects on water and soil in the Tatra National Park were studied.

The study areas were two valleys – Malá Studená, accessible by trail from south with higher human impact and visitation, including mountain huts Téryho and Zamkovského chata and Javorová, accessible from the northern part with a low number of visitors. Soil samples were taken from the main path, 30 cm away from it and water samples from or near the main path in both valleys. The selected colonies, after the cultivation on TSA medium were also analysed according to the dry and semi-extraction procedure of MALDI–TOF method. Most of the obtained strains are endospore forming, psychrotolerant species like Pseudomonas, Bacillus or Paenibacillus away of path, which corresponds with the climate and geographical conditions. But, the relatedness of soil sample strains in both valleys increases with rising altitude, with distance away from path; in contrast, the relatedness of water samples strains in both valleys increases with increasing distance sample areas from chalet and frequent visitors’ places. Water and soil samples were processed for community level physiological profiling using Biolog EcoPlates. The obtained results of carbon source utilization abilities of bacterial communities in both valleys suggested lower diversity in Javorová Valley, which corresponds probably with less visitor intensity, with less anthropogenic impact as well as with less risk of xenobiotics presence in environment.