Biofilm formation is a key virulence factor for a wide range of microorganisms that cause chronic infections. The multifactorial nature of biofilm development and drug tolerance imposes great challenges for the use of conventional antimicrobials and indicates the need for multi-targeted or combinatorial therapies. In this Review, we focus on current therapeutic strategies and those under development that target vital structural and functional traits of microbial biofilms and drug tolerance mechanisms, including the extracellular matrix and dormant cells. We emphasize strategies that are supported by in vivo or ex vivo studies, highlight emerging biofilm-targeting technologies and provide a rationale for multi-targeted therapies aimed at disrupting the complex biofilm microenvironment.

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Targeting microbial biofilms: current and prospective therapeutic strategies.

The dynamic and polymicrobial oral microbiome is a direct precursor of diseases such as dental caries and periodontitis, two of the most prevalent microbially induced disorders worldwide. Distinct microenvironments at oral barriers harbour unique microbial communities, which are regulated through sophisticated signalling systems and by host and environmental factors. The collective function of microbial communities is a major driver of homeostasis or dysbiosis and ultimately health or disease. Despite different aetiologies, periodontitis and caries are each driven by a feedforward loop between the microbiota and host factors (inflammation and dietary sugars, respectively) that favours the emergence and persistence of dysbiosis. In this Review, we discuss current knowledge and emerging mechanisms governing oral polymicrobial synergy and dysbiosis that have both enhanced our understanding of pathogenic mechanisms and aided the design of innovative therapeutic approaches for oral diseases.

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The oral microbiota: dynamic communities and host interactions.

Fungi of the genus Trichoderma are soilborne, green-spored ascomycetes that can be found all over the world. They have been studied with respect to various characteristics and applications and are known as successful colonizers of their habitats, efficiently fighting their competitors. Once established, they launch their potent degradative machinery for decomposition of the often heterogeneous substrate at hand. Therefore, distribution and phylogeny, defense mechanisms, beneficial as well as deleterious interaction with hosts, enzyme production and secretion, sexual development, and response to environmental conditions such as nutrients and light have been studied in great detail with many species of this genus, thus rendering Trichoderma one of the best studied fungi with the genome of three species currently available. Efficient biocontrol strains of the genus are being developed as promising biological fungicides, and their weaponry for this function also includes secondary metabolites with potential applications as novel antibiotics. The cellulases produced by Trichoderma reesei, the biotechnological workhorse of the genus, are important industrial products, especially with respect to production of second generation biofuels from cellulosic waste. Genetic engineering not only led to significant improvements in industrial processes but also to intriguing insights into the biology of these fungi and is now complemented by the availability of a sexual cycle in T. reesei/Hypocrea jecorina, which significantly facilitates both industrial and basic research. This review aims to give a broad overview on the qualities and versatility of the best studied Trichoderma species and to highlight intriguing findings as well as promising applications.

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Biology and biotechnology of Trichoderma

Secondary thickening in pteridophytes.-The known cases of secondary thickening in recent Pteridophyta have been brought together by HILL23 in a useful resume. After stating the criteria for secondary growth, Botrychium, which has a distinct cambium, and Ophioglossum, which lacks a definite layer, are described, followed by Angiopteris and Marattia, in which a cambium forms a few xylem elements. CORMACK'S observations on the secondary wood in the nodes of Equisetum are cited, though no reference is made to the cambium in the young cone as reported by J]FFREY.24 The other cases of secondary growth include Psilotum, Selaginella spinulosa, and several species of Isoetes, especially I. hystrix, which may show a cambium outside the vascular cylinder.-M. A.

The Cell Wall

Isolated from a wide range of sources, the genus Paenibacillus comprises bacterial species relevant to humans, animals, plants, and the environment. Many Paenibacillus species can promote crop growth directly via biological nitrogen fixation, phosphate solubilization, production of the phytohormone indole-3-acetic acid (IAA), and release of siderophores that enable iron acquisition. They can also offer protection against insect herbivores and phytopathogens, including bacteria, fungi, nematodes, and viruses. This is accomplished by the production of a variety of antimicrobials and insecticides, and by triggering a hypersensitive defensive response of the plant, known as induced systemic resistance (ISR). Paenibacillus-derived antimicrobials also have applications in medicine, including polymyxins and fusaricidins, which are nonribosomal lipopeptides first isolated from strains of Paenibacillus polymyxa. Other useful molecules include exo-polysaccharides (EPS) and enzymes such as amylases, cellulases, hemicellulases, lipases, pectinases, oxygenases, dehydrogenases, lignin-modifying enzymes, and mutanases, which may have applications for detergents, food and feed, textiles, paper, biofuel, and healthcare. On the negative side, Paenibacillus larvae is the causative agent of American Foulbrood, a lethal disease of honeybees, while a variety of species are opportunistic infectors of humans, and others cause spoilage of pasteurized dairy products. This broad review summarizes the major positive and negative impacts of Paenibacillus: its realised and prospective contributions to agriculture, medicine, process manufacturing, and bioremediation, as well as its impacts due to pathogenicity and food spoilage. This review also includes detailed information in Additional files 1, 2, 3 for major known Paenibacillus species with their locations of isolation, genome sequencing projects, patents, and industrially significant compounds and enzymes. Paenibacillus will, over time, play increasingly important roles in sustainable agriculture and industrial biotechnology.

https://link.springer.com/content/pdf/10.1186%2Fs12934-016-0603-7.pdf

Current knowledge and perspectives of Paenibacillus : a review

The aerial parts of selected Potentilla species (P. anserina, P. argentea, P. erecta, P. fruticosa, P. grandiflora, P. nepalensis, P. norvegica, P. pensylvanica, P. crantzii and P. thuringiaca) were investigated in order to determine their contents of polyphenolic compounds. The results showed that P. fruticosa has relatively high concentrations of tannins (167.3 ± 2.0 mg/g dw), proanthocyanidins (4.6 ± 0.2 mg/g dw) and phenolic acids (16.4 ± 0.8 mg/g dw), as well as flavonoids (7.0 ± 1.1 mg/g dw), calculated as quercetin. Furthermore, we investigated the in vitro inhibitory effects of aqueous extracts from these species against cariogenic Streptococcus spp. strains. It was found that the tested samples moderately inhibit the growth of oral streptococci. However, all the preparations exhibited inhibitory effects on water-insoluble α-(1→3)-, α-(1→6)-linked glucan (mutan) and artificial dental plaque formation. The extract from P. fruticosa showed the highest anti-biofilm activities, with minimum mutan and biofilm inhibition concentrations of 6.25–25 and 50–100 µg/mL, respectively. The results indicate that the studied Potentilla species could be a potential plant material for extracting biologically active compounds, and could become a useful supplement for pharmaceutical products as a new anticariogenic agent in a wide range of oral care products.

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Variation in total polyphenolics contents of aerial parts of Potentilla species and their anticariogenic activity.

To show biological activity of carboxymethylated α-(1 → 3)-d-glucans isolated from the selected macromycetes fungi on human tumor and normal cells. Water-insoluble, alkali-soluble polysaccharides (WIP) were isolated from fruiting bodies of four macromycetes fungi: Lentinus edodes, Pleurotus ostreatus, Piptoporus betulinus and Laetiporus sulphureus. The structure of the polysaccharides was determined using composition analysis, methylation analysis, fourier transform infrared spectroscopy, and nuclear magnetic resonance spectroscopy. The chemical and spectroscopic investigations indicated that the polysaccharides were an α-(1 → 3)-d-glucans. A biological activity analysis of the carboxymethylated (CM) α-(1 → 3)-d-glucans was based on an assessment of their cytotoxic, mitochondrial metabolism-modulating, and free radical scavenging effects. The cytotoxic activity of the CM-glucans was concentration- and cell-type-dependent. The tested CM-glucans, generally, did not have a free radical scavenging effect. The CM-α-(1 → 3)-d-glucans isolated from the selected macromycetes fungi are biologically active and may therefore be used as diet or therapy supplements.

/pdf/a-1-3-d-glucans-from-fruiting-bodies-of-selected-51xl4atkyz.pdf

α-(1 → 3)-D-glucans from fruiting bodies of selected macromycetes fungi and the biological activity of their carboxymethylated products.

Fourier transform infrared (FT-IR) and Raman spectroscopy and mapping were applied to the analysis of biofilms produced by bacteria of the genus Streptococcus. Bacterial biofilm, also called dental plaque, is the main cause of periodontal disease and tooth decay. It consists of a complex microbial community embedded in an extracellular matrix composed of highly hydrated extracellular polymeric substances and is a combination of salivary and bacterial proteins, lipids, polysaccharides, nucleic acids, and inorganic ions. This study confirms the value of Raman and FT-IR spectroscopies in biology, medicine, and pharmacy as effective tools for bacterial product characterization.

https://www.mdpi.com/1422-0067/21/11/3811/pdf

Małgorzata Pleszczyńska

Papers

Variation in total polyphenolics contents of aerial parts of Potentilla species and their anticariogenic activity.

α-(1 → 3)-D-glucans from fruiting bodies of selected macromycetes fungi and the biological activity of their carboxymethylated products.

The FT-IR and Raman Spectroscopies as Tools for Biofilm Characterization Created by Cariogenic Streptococci

(1→3)-α-D-Glucan hydrolases in dental biofilm prevention and control: A review.

Chemical characterization of a water insoluble (1→3)-α-D-glucan from an alkaline extract of Aspergillus wentii.