Biophysical and biological characterisation of collagen/resilin-like protein composite fibres.

Collagen type I, in various physical forms, is widely used in tissue engineering and regenerative medicine. To control the mechanical properties and biodegradability of collagen-based devices, exogenous cross-links are introduced into the 3D supramolecular structure. However, potent cross-linking methods are associated with cytotoxicity, whilst mild cross-linking methods are associated with suboptimal mechanical resilience. Herein, we assessed the influence of resilin, a super-elastic and highly stretchable protein found within structures in arthropods where energy storage and long-range elasticity are needed, on the biophysical and biological properties of mildly cross-linked extruded collagen fibres. The addition of resilin-like protein in the 4-arm poly(ethylene glycol) ether tetrasuccinimidyl glutarate cross-linked collagen fibres resulted in a significant increase of stress and strain at break values and a significant decrease of modulus values. The addition of resilin-like protein did not compromise cell metabolic activity and DNA concentration. All groups are supported parallel to the longitudinal fibre axis cell orientation. Herein we provide evidence that the addition of resilin-like protein in mildly cross-linked collagen fibres improves their biomechanical properties, without jeopardising their biological properties.

[The microbial transformation of phenanthrene and anthracene].

The transformation of phenanthrene and anthracene by Rhodococcus rhodnii 135, Pseudomonas fluorescens 26K, and Arthrobacter sp. K3 is studied. Twenty-one intermediates of phenanthrene and anthracene transformation are identified by HPLC, mass spectrometry, and NMR spectroscopy. P. fluorescens 26K and Arthrobacter sp. K3 are found to produce a wide range of intermediates, whereas R. rhodnii 135 oxidizes phenanthrene, resulting in the formation of a sole product, 3-hydroxyphenanthrene. Putative transformation pathways of phenanthrene and anthracene are proposed for the three bacterial strains studied. These strains can be used to obtain valuable compounds (such as hydroxylated polycyclic aromatic hydrocarbons) that are difficult to produce by chemical synthesis.

[Fluorene cometabolism by Rhodococcus rhodochrous and Pseudomonas fluorescens]. / Kometabolizm fluorena kul'turami Rhodococcus rhodochrous i Pseudomonas fluorescens.

The transformation of fluorene by Rhodococcus rhodochrous strain 172 grown on sucrose and Pseudomonas fluorescens strain 26K grown on glycerol was studied as a function of the substrate concentration and the growth phase. Under certain cultivation conditions, fluorene was completely consumed from the medium. The specific transformation rate of fluorene was considerably higher when it was transformed in the presence of the cosubstrates than when it served as the sole carbon source. An approach to the evaluation of the specific transformation rate of fluorene during batch cultivations is proposed.

[Fluorene degradation by bacteria of the genus Rhodococcus]. / Prevrashchenie fluorena bakteriiami roda Rhodococcus.

Of the four investigated Rhodococcus strains (R. rhodochrous 172, R. opacus 4a and 557, and R. rhodnii 135), the first three strains were found to be able to completely transform fluorene when it was present in the medium as the sole source of carbon at a concentration of 12-25 mg/l. At a fluorene concentration of 50-100 mg/l in the medium, the rhodococci transformed 50% of the substrate in 14 days. The addition of casamino acids and sucrose (1-5 g/l) stimulated fluorene transformation, so that R. rhodochrous 172 could completely transform it in 2-5 days. Nine intermediates of fluorene transformation were isolated, purified, and structurally characterized. It was found that R. rhodnii 135 and R. opacus strains 4a and 557 hydroxylated fluorene with the formation of 2-hydroxyfluorene and 2,7-dihydroxyfluorene. R. rhodochrous 172 transformed fluorene via two independent pathways to a greater degree than did the other rhodococci studied.

[Dependence of transformation of chlorophenols by Rhodococci on position and number of chlorine atoms in the aromatic ring]. / Zavisimost' prevrashcheniia khlorfenolov rodokokkami ot polozheniia i chisla atomov khlora v aromaticheskom kol'tse.

Study of the conversion of chlorophenols by Rhodococcus opacus 1G, R. rhodnii 135, R. rhodochrous 89, and R. opacus 1cp disclosed the dependence of the conversion rate and pathway on the number and position of chlorine atoms in the aromatic ring. The most active chlorophenol converter, strain R. opacus 1cp, grew on each of the three isomeric monochlorophenols and on 2,4-dichlorophenol; the rate of growth decreased from 4-chlorophenol to 3-chlorophenol and then to 2-chlorophenol. The parameters of growth on 2,4-dichlorophenol were the same as on 3-chlorophenol. None of the strains studied utilized trichlorophenols. A detailed study of the pathway of chlorophenol transformation showed that 3-chloro-, 4-chloro-, and 2,4-dichlorophenol were utilized by the strains via a modified ortho-pathway. 2-Chlorophenol and 2,3-dichlorophenol were transformed by strains R. opacus 1cp and R. rhodochrous 89 via corresponding 3-chloro- and 3,4-dichloropyrocatechols, which were then hydroxylated with the formation of 4-chloropyrogallol and 4,5-dichloropyrogallol; this route had not previously been described in bacteria. Phenol hydroxylase of R. opacus 1G exhibited a previously undescribed catalytic pattern, catalyzing oxidative dehalogenation of 2,3,5-trichlorophenol with the formation of 3,5-dichloropyrocatechol but not hydroxylation of the nonsubstituted position 6.

[Role of coryneform bacteria in the degradation of ordram in a reservoir]. / Rol' korinepodobnykh bakterii v degradatsii ordrama v vodoeme.

The object of the work was to study the role of coryneform microorganisms in the degradation of residues of ordram, a thiocarbamate herbicide. Only rhodococci were found to play an essential role in the process among these bacteria. Rhodococci actively oxidized the herbicide if its concentration was several milligrams per litre though its high concentrations (over 100 mg/l) inhibited the growth of the bacteria. This group of microorganisms, together with bacilli and certain cocci, belongs to the most active part of saprophytic microflora which transforms the molecule of the original herbicide yielding keto and hydroxy derivatives, sulfoxide, products of S-dealkylation and cleavage of the hexamethyleneimine ring. The incidence of rhodococci remains at a high level if the appropriate cosubstrates are added. In the conditions of rice check plots, rhodococci can play an essential role in the degradation of the herbicide.

[Degradation of herbicide Alvison-8 by microorganisms]. / Degradatsiia gerbitsida alvison-8 mikroorganizmami

Microbial degradation of a new herbicide, Alvison-8, was studied. No strains capable of growth at the account of this compound as a source of carbon have been found among microorganisms isolated from soil treated with the herbicide and among collection cultures. Some strains can degrade Alvison-8 at a concentration of 100-300 mg/litre in cooxidative conditions. Effective cosubstrates are such compounds which are actively metabolized by microorganisms but cannot maintain intensive growth. In some cases, the cultures grew at the account of cosubstrates and the process consisted of two stages, i. e. degradation occured at the beginning prior to the phase of active growth.

[Intensity of bacterial methane formation in ooze deposits in lakes]. / Intensivnost' bakterial'nogo metanoobrazovaniia v ilovykh otlozheniiakh nekotorykh ozer

The rate of methane production of bacteria via the decomposition of acetate in ooze deposits of the Mari lakes was 0.0165 to 0.483 mg CH4/day/ litre wet ooze. From 32 to 98 per cent of methane in the ooze of studied reservoirs formed through microbiological reduction of carbon dioxide by hydrogen.