The effect of norepinephrine as a compound modulating the activity of the antibiotic azithromycin on single-species and binary biofilms of members of the human microbiota, Staphylococcus aureus and Kytococcus schroeteri, was studied in various model systems. At the concentration of 3.55 µM, the hormone was shown to be able, depending on the cultivation system and incubation time, of both enhancing and weakening the effects of azithromycin at subinhibitory concentrations (0.001 and 4 µg/mL). In the case of rapidly formed biofilms, norepinephrine weakened the inhibitory effect of the antibiotic, while in the presence of the full stage of adhesion the hormone, on the contrary, enhanced the inhibitory effect. Interaction between two microorganisms in the community was no less important, since the presence of K. schroeteri in the community changed the effect of azithromycin (4 μg/mL) in combination with norepinephrine on S. aureus. It was shown that azithromycin and norepinephrine, as well as their combinations, were able to change the expression of the genes coding resistance not only to macrolides (increased expression of the mrx gene by a combination of 4 μg/mL azithromycin and 3.55 μM norepinephrine), but also to fluoroquinolones (decreased expression of the arlR gene and increased one of mdtK).

Transcriptomic and proteomic analysis were performed on 72 h biofilms of the acneic strain Cutibacterium acnes and planktonic cultures in the presence of epinephrine. Epinephrine predominantly downregulated genes associated with various transporter proteins. No correlation was found between proteomic and transcriptomic profiles. In control samples, the expression of 51 proteins differed between planktonic cultures and biofilms. Addition of 5 nM epinephrine reduced this number, and in the presence of 5 µM epinephrine, the difference in proteomic profiles between planktonic cultures and biofilms disappeared. According to the proteomic profiling, epinephrine itself was more effective in the case of C. acnes biofilms and potentially affected the tricarboxylic acid cycle (as well as alpha-ketoglutarate decarboxylase Kgd), biotin synthesis, cell division, and transport of different compounds in C. acnes cells. These findings are consistent with recent research on Micrococcus luteus, suggesting that the effects of epinephrine on actinobacteria may be universal.

A simple and efficient method for obtaining monospecies and binary Staphylococcus aureus and Staphylococcus epidermidis cultures in sodium alginate gel matrix mimicking the natural microenvironment of the nasal cavity was proposed. The cultures were used for studying the effect of norepinephrine on monospecies and binary communities of two types of bacteria, S. aureus (invasive strain) and S. epidermis (commensal strain). After 24-h incubation, S. aureus predominated in the binary community, but later it was replaced by S. epidermis. Norepinephrine at higher concentrations accelerated this process without principally changing it. The model can be used to develop more effective complex antimicrobial drugs.

Natriuretic peptides (NP) are able to affect biofilms of human commensal microorganisms, including representatives of the genus Staphylococcus, however, the literature lacks data on the molecular changes caused by these hormones at the posttranslational level. In this regard, the present work shows for the first time that C-type natriuretic peptide (CNP) induces large changes in protein profiles of Staphylococcus aureus cells and biofilms. The presence of the hormone leads to a more pronounced difference in protein profiles between planktonic cells and biofilms when compared to control pairs of samples. The main processes affected are TCA cycle, protein transport, purine synthesis (decrease in the amount of the corresponding proteins in biofilms) and nitrate metabolism (increase in the amount of nitrogenases and other proteins in biofilms). It is necessary to mention separately the decreased amount of lysostaphin in biofilms compared to planktonic cultures when exposed to CNP. This may be one of the potential mechanisms of the recently shown reduction of competitive properties of S. epidermidis in the community with other microorganisms, which is induced by the presence of CNP in the medium. In addition, the results of the study strengthen the hypothesis that, as in the case of other human hormones, the action of CNP on S. epidermidis , is multitargeted. One of the likely mechanisms of the hormone’s action may be the disruption of the transition from planktonic culture to biofilm, which can be assumed without suppressing cell growth, which needs further verification.

Human organism is tightly interconnected with its microbiota on physiological and signaling levels. Microbial endocrinology as an interdisciplinary area of studying host–microbiota interactions can focus on either player: how the microbiota affects the host via synthesis of host-targeted humoral factors and how the host-derived molecules regulate the microbial community homeostasis. The present mini-review presents the authors' perspective on the impact of human hormones on the microbiota. It discusses known effects, but especially outlines existing complications in this research area, and proposes directions for future investigation.

Although natriuretic peptides (NP) may affect the biofilms of human commensal microorganisms, including members of the genus Staphylococcus, no literature data on molecular changes caused by these hormones at the posttranslational level are available. The present work is the first report on noticeable changes in protein profiles of Staphylococcus epidermidis cells and biofilms caused by the C-type natriuretic peptide (CNP). The presence of the hormone caused a more pronounced difference in protein profiles between planktonic cells and biofilms compared to the control pairs of samples. The main processes affected were the TCA cycle, protein transport, purine synthesis (decreased content of the relevant proteins in biofilms) and nitrate metabolism (increased content of nitrogenases and other proteins in biofilms). Decreased content of lysostaphin in biofilms compared to planktonic cultures caused by exposure to CNP should be mentioned specifically. This may be one of the potential mechanisms of the recently shown decreased competitiveness of S. epidermidis in communities with other microorganisms, which is induced by the presence of CNP in the medium. Moreover, our results support the hypothesis that, as in the case of other human hormones, the effect of CNP on S. epidermidis is multitargeted. One of the likely mechanisms of the action of the hormone may be the disruption of transition from planktonic culture to the biofilm, which can be assumed without suppressing cell growth, which needs further verification.

A series of biocide-containing polyethylene composites were obtained using novel guanidine-containing copolymers immobilized on an inert mineral carrier. Multispecies microbial communities were isolated from the surface of polyethylene samples either incubated or found in the environment, and their taxonomic composition was determined. Biofilms reconstructed using microorganisms obtained from different ecotopes were shown to intensively foul polyethylene surfaces. The presence of polyguanidine biocide suppressed the growth and survival of both binary and multispecies biofilms, with a cumulative effect during long-term incubation. When microorganisms were co-cultivated in binary biofilms, the phenomenon of a decrease in biocide effectiveness was demonstrated. This protective effect is potentially based on cooperative interactions inside the binary biofilm community. Scanning electron microscopy showed a pronounced difference in the architecture of reconstructed biofilms incubated in the presence of biocide in comparison to control samples, where biocide suppressed the formation of dense and well-organized three-dimensional structures. Biofilm disruption by immobilized biocides occurred primarily during the later stages of biofilm formation, probably caused by polycation interaction with their negatively charged extracellular components.

The effect of C-type natriuretic peptide in a concentration closer to the normal level in human blood plasma was studied on the mono-species and dual-species biofilms of the skin commensal bacteria Cutibacterium acnes HL043PA2 and Staphylococcus epidermidis ATCC14990. Despite the marginal effect of the hormone on cutibacteria in mono-species biofilms, the presence of staphylococci in the community resulted in a global shift of the CNP effect, which appeared to increase the competitive properties of C. acnes, its proliferation and the metabolic activity of the community. S. epidermidis was mostly inhibited in the presence of CNP. Both bacteria had a significant impact on the gene expression levels revealed by RNA-seq. CNP did not affect the gene expression levels in mono-species cutibacterial biofilms; however, in the presence of staphylococci, five genes were differentially expressed in the presence of the hormone, including two ribosomal proteins and metal ABC transporter permease. In staphylococci, the Na-translocating system protein MpsB NADH-quinone oxidoreductase subunit L was downregulated in the dual-species biofilms in the presence of CNP, while in mono-species biofilms, two proteins of unknown function were downregulated. Hypothetically, at least one of the CNP mechanisms of action is via the competition for zinc, at least on cutibacteria.

In the current study, extensive Orbitrap mass spectrometry analysis was conducted for skin strain Micrococcus luteus C01 planktonic cultures and biofilms after 24 h and 72 h of incubation either in the presence of epinephrine or without any implementations. The investigation revealed the complex and conditionally extensive effect of epinephrine at concentrations closer to normal blood plasma concentrations on both planktonic cultures and biofilms of skin strain M. luteus C01. The concentrations of hundreds of proteins changed during the shift from planktonic growth mode to biofilm and hundreds of proteins were downregulated or upregulated in the presence of epinephrine. Ribosomal, TCA, and cell division proteins appear to be the most altered in their amounts in the presence of the hormone. Potentially, the regulatory mechanism of this process is connected with c-di-GMP and histidine kinases, which were affected by epinephrine in different samples. The phenomenon of epinephrine-based biofilm regulation in M. luteus C01 has wide implications for microbial endocrinology and other research areas.

It has been established that the human atrial natriuretic peptide is able to alter the effect of azithromycin on Kytococcus schroeteri H01 and Staphylococcus aureus 209P monospecies and binary biofilms. The effect of the hormone depends on the surface type and cultivation system, and it may have both enhancing and counteracting effects. The antagonistic effect of the hormone was observed mostly on hydrophobic surfaces, whereas the additive effect was observed on hydrophilic surfaces like glass. Also, the effect of the hormone depends on the antibiotic concentration and bacterial species. The combination of azithromycin and ANP led to an amplification of cell aggregation in biofilms, to the potential increase in matrix synthesis, and to a decrease in S. aureus in the binary community. Also, ANP, azithromycin, and their combinations caused the differential expression of genes of resistance to different antibiotics, like macrolides (mostly increasing expression in kytococci), fluoroquinolones, aminoglycosides, and others, in both bacteria.

Localization and structural organization of microbial biofilms developing in anthropogenic ecological niches of meat-processing plants using different raw materials (poultry, pork, or mixed materials) were investigated. Mature biofilms were revealed both at the sites subject to routine sanitary control (equipment, sewage traps, and walls) and at other locations (ceilings, reverse (lower) side of bridges, vehicle wheels, and tunnel walls at subzero temperatures), indicating high adaptability of microbial communities. This finding indicates the urgency of modification (extension) of the list of cleansing sites and of the relevant protocols. The information on the composition and diversity of microbial biofilms in this ecotope, as well as on the physiological state of component microorganisms (e.g., active, dormant, and lysing cells) was obtained using transmission electron microscopy. The morphotypes facilitating bacterial survival in these biofilms were described (old cells and several types of specialized dormant forms).

— Investigation of the interactions between Staphylococcus aureus 209P and Kytococcus schroeteri H01 in binary biofilms revealed the sensitivity of these bacteria to the atrial natriuretic peptide (ANP) in a concentration of 6.5 × 10 –10 M. In the presence of ANP, affinity of both bacteria to hexadecane decreased significantly, as was determined by MATS (microbial adhesion to solvents) experiments. Their ability to aggregate with each other and on the surface also altered in the presence of the hormone, affecting mainly the initial adhesion stage in biofilm formation. Plating of the binary communities revealed that they consisted mostly of staphylococci, while K. schroeteri constituted the minor part of the cell biomass. They, however, affected cell aggregation and the ANP effect on the community. K. schroeteri played a dualistic role, both facilitating S. aureus adhesion and acting as its antagonist in the biofilm. Moreover, in binary communities K. schroeteri was responsible for the shift of ANP action on S. aureus from neutral/stimulatory to inhibitory.

Biofilms are microbial communities of cells embedded in extracellular matrix, and they are regarded as a major form of the natural and laboratory occurrence of bacteria. Cutaneous microbiota is represented by prokaryotic and eukaryotic organisms, which form biofilms in the different niches including the skin surface, glands, and hair follicles. Despite of a large number of in vitro studies dedicated to the biofilms of cutaneous bacteria, the methods used usually do not closely take into account the specific surroundings of certain skin parts. In this study, we introduce a new simple method of biofilm cultivation on the solid keratine/agarose pellets embedded in polyacrylamide gel. In such a model system, we tried to minimize the amount of liquid phase, which makes a model close to a human comedo, and provide a prominent biofilm formation of selected cutaneous bacteria.

This study aimed to investigate the dependence of the biocidal activity of polyguanidine (co)polymers on their structure during the formation of biofilms by active PE-degrading cultures of model microorganisms. The Bc-2 copolymer of methacryloyl guanidine hydrochloride (MGHC) and diallyldimethylammonium chloride (DADMAC), which suppressed both the formation of biofilms and the growth of planktonic cultures, exhibited the highest activity. When PE was exposed in tropical soil, the composition of the microbial community on the PE surface differed significantly from that of the community in the surrounding soil. In particular, the proportion of Actinobacteria increased from 7% to 29%, while the proportion of Bacteroidetes decreased from 38% to 8%. Keywords: biofilms, polyhexamethylene guanidine salts, dynamics of biofilm formation, antibiofilm effect, composite materials

The importance of the impact of human hormones on commensal microbiota and microbial biofilms is established in lots of studies. In the present investigation, we continued and extended the research of epinephrine effects on the skin commensal Micrococcus luteus C01 and its biofilms, and also the matrix changes during the biofilm growth. Epinephrine in concentration 4.9 × 10–9 M which is close to normal blood plasma level increased the amount of polysaccharides and extracellular DNA in the matrix, changed extensively its protein, lipid and polysaccharide composition. The Ef-Tu factor was one of the most abundant proteins in the matrix and its amount increased in the presence of the hormone. One of the glucose-mannose polysaccharide was absent in the matrix in presence of epinephrine after 24 h of incubation. The matrix phospholipids were also eradicated by the addition of the hormone. Hence, epinephrine has a great impact on the M. luteus biofilms and their matrix composition, and this fact opens wide perspectives for the future research.

The effect of humic acids on the formation of multispecies biofilms on the surface of high-pressure polyethylene and on the initial stages of its biocorrosion has been studied. The ability to form biofilms on the polyethylene surface and the initial stages of its biodegradation have been analyzed for two bacterial communities (binary and multispecies) isolated from the surface of polyethylene incubated in the topsoil (0–5-cm layer) in Myanmar during 180 days. Polyethylene samples were transported under sterile conditions to a laboratory (Moscow) and placed in vials with liquid medium (LB diluted 50 times by mineral medium M9 and with 0.1% C11–C16 paraffin solution added as an additional carbon source). Cultures were then disseminated to obtain individual colonies. Humic acids were extracted by alkaline extraction from the upper horizons of ferrallitic soil, in which the polyethylene sample was incubated (Myanmar), and from typical chernozem sampled in Lipetsk oblast (Orthic Acrisol and Haplic Chernozem according to the World Reference Base for Soil Resources, 2014). Humic acids were extracted from humate fertilizer Fleksom based on lowland peat. We assessed the formation of biofilms on the polyethylene surface by staining with crystal violet and changes in the polyethylene surface after the removal of biofilms by densitometric method. The stimulating effect of humic acids of a wide concentration range on the biofilm growth on the polyethylene surface and at the initial stage of its biodegradation has been revealed for the first time. The methodological approaches and the results obtained supplement the information on polyethylene biodegradation and can be applied in biotechnologies.

The distribution, colonization, and biodegradation of primary and secondary microplastics, as well as were effect on the plastisphere ecological systems, are analyzed. The pathways of microplastic contamination of the atmosphere, hydrosphere, and lithosphere are described. The composition of multispecies communities colonizing the microplastics and their differences from environmental communities unassociated with plastic within the same habitat are considered. The processes of microplastic biodegradation and their role as vectors for transfer of genetic information affecting the structure of natural microbial communities and for the propagation of toxic components are discussed.