The plant pathogenic bacterium Clavibacter michiganense ssp. nebraskense secretes an anion channel forming activity (CFA) into the culture field. The CFA inserts spontaneously into planar lipid membranes when culture fluid of this species is added to the aqueous phase of the bilayer chamber. The channels formed are highly anion selective. The conductance decreases for larger anions (Cl- greater than SCN- greater than SO2-(4] and is practically zero for gluconate. The channels show a unique voltage dependence: (i) The single-channel conductance increases linearly with voltage up to 200 mV saturating at 250 mV with 25 +/- 1 pS (300 mM KCl). The channel is closed at negative voltage relative to the side of insertion (diode-type I-V curve). (ii) The average number of open channels also increases with voltage. The Poisson distribution of channel numbers indicates independent opening of the channels. Channel activity can be abolished by protease treatment of the planar bilayer. The channels can be blocked by indanyloxyacetic acid (IAA-94) and by pH greater than 10. The CFA was purified yielding one major band on the SDS gel with a relative molecular mass of 65,000. The putative involvement of the CFA in the toxicity of this plant pathogen is discussed and compared to other toxins like colicins and to the diptheria toxin group.
Methanotrophs were present in 48 of 225 stone samples which were removed from 19 historical buildings in Germany and Italy. The average cell number of methanotrophs was 20 CFU per g of stone, and their activities ranged between 11 and 42 pmol of CH4 g of stone−1 day−1. Twelve strains of methane-oxidizing bacteria were isolated. They belonged to the type II methanotrophs of the genera Methylocystis,Methylosinus, and Methylobacterium. In masonry, growth substrates like methane or methanol are available in very low concentrations. To determine if methane could be produced by the stone at rates sufficient to support growth of methanotrophs, methane production by stone samples under nonoxic conditions was examined. Methane production of 0.07 to 215 nmol of CH4 g of stone−1 day−1 was detected in 23 of 47 stone samples examined. This indicated the presence of the so-called “mini-methane”-producing bacteria and/or methanogenic archaea. Methanotrophs occurred in nearly all samples which showed methane production. This finding indicated that methanotrophs depend on biogenic methane production in or on stone surfaces of historical buildings.
Extended AbstractIm Rahmen des BMFT-Projektes ,,SteinLerfall" wurden 112 Mortelproben von 16 verschiedenen historischen Gebauden untersucht. Die Zellzahlen von Nitrifikanten, methylotrophen und heterotrophen Bakterien sowie Pilzen wurden mittels der MPN und Koch'schen Plattentechnik hestimrnt. Stoffwechsclaktivitaten von Nitrifikanten und die Konzentrationen anorganischer Stickstoffsalze wurden durch die HPLC an RP-18 Saulen ermittelt. Die erhaltenen Daten wurden mit denen von Natursteinprobeii verglichen.
Zusammenfassung
Die statistische Auswertung ausgewählter biologischer und beschreibender Parameter von Proben des Breisacher Münsters zeigte einen deutlichen Zusammenhang zwischen dem Auftreten von Schalen und dem Bewuchs mit Nitrifikanten. In der Vorstufe dieses Schadensbildes, der Klasse "Abbröckeln bis Schalenbildung", konnten diese Organismen in großen Mengen nachgewiesen werden. In der fertig ausgebildeten Schale waren sie dann wieder auf der neuen Oberfläche unterhalb der Schale zu finden. Für spätere Restaurationen sollten Ersatzmaterialien auf ihre Eignung zum mikrobiellen Bewuchs getestet werden. Roter Tuff am Breisacher Münster war am stärksten durch Nitrifikanten gefährdet. Dieses Baumaterial aus Restaurationen des 19. Jahrhunderts hat sich als ungeeignet erwiesen. Weiterhin zeigen die Daten daß Kaiserstühler Tuff, im Vergleich mit Naturstein, heterotrophen Organismen gute Wachstumsbedingungen bietet. Eine Ursache hierfür ist wahrscheinlich die hohe Wasseraufnahmekapazität (große innere Oberfläche).
RESUMO Neste estudo foi avaliada a atividade antibacteriana de fibras têxteis contendo nanopartículas de poli(óxido de etileno-b-ácido lático) com óleos essenciais incorporados. O sistema desenvolvido demonstrou atividade antibacteriana contra Staphylococcus aureus, sugerindo seu potencial uso como agente antibacteriano. Foram utilizados copolímeros dibloco baseados em um bloco fixo de PEO (5kDa) e dois segmentos de PLA diferentes (4,5 e 10kDa). A morfologia, a eficiência do encapsulamento, a interação da blenda de óleos essenciais (incluindo, lavanda, melaleuca, tomilho, cravo, cedro e capim limão) e polímero e a cinética de liberação do agente ativo nas nanopartículas foram avaliadas. O raio hidrodinâmico das nanopartículas determinado pela dispersão da luz foi afetado pelo tamanho do bloco de poli(ácido lático). A liberação in vitro sugere que a barreira polimérica é capaz de controlar a liberação de óleo. A atividade antibacteriana foi mais eficaz em tecidos com fibras arranjadas aleatoriamente. De acordo com estudos da literatura, nanopartículas obtidas de copolímeros com menor massa molar de PLA favoreceram a liberação da mistura de óleos essenciais. O processo de incorporação dos óleos essenciais nas fibras têxteis mostrou-se eficiente sugerindo viabilidade quanto ao uso desse sistema no controle antibacteriano. Os sistemas desenvolvidos oferecem uma nova estratégia para a liberação controlada com atividade antibacteriana e apresentam potenciais aplicações na indústria calçadista.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.