Bark-dwelling methanotrophic bacteria decrease methane emissions from trees.

Tree stems are an important and unconstrained source of methane, yet it is uncertain whether internal microbial controls (i.e. methanotrophy) within tree bark may reduce methane emissions. Here we demonstrate that unique microbial communities dominated by methane-oxidising bacteria (MOB) dwell within bark of Melaleuca quinquenervia, a common, invasive and globally distributed lowland species. In laboratory incubations, methane-inoculated M. quinquenervia bark mediated methane consumption (up to 96.3 µmol m-2 bark d-1) and reveal distinct isotopic δ13C-CH4 enrichment characteristic of MOB. Molecular analysis indicates unique microbial communities reside within the bark, with MOB primarily from the genus Methylomonas comprising up to 25 % of the total microbial community. Methanotroph abundance was linearly correlated to methane uptake rates (R2 = 0.76, p = 0.006). Finally, field-based methane oxidation inhibition experiments demonstrate that bark-dwelling MOB reduce methane emissions by 36 ± 5 %. These multiple complementary lines of evidence indicate that bark-dwelling MOB represent a potentially significant methane sink, and an important frontier for further research.

Transcriptome Profiling of Melaleuca quinquenervia Challenged by Myrtle Rust Reveals Differences in Defense Responses Among Resistant Individuals.

Plants have developed complex defense mechanisms to protect themselves against pathogens. A wide-host-range fungus, Austropuccinia psidii, which has caused severe damage to ecosystems and plantations worldwide, is a major threat to Australian ecosystems dominated by members of the family Myrtaceae. In particular, the east coast wetland foundation tree species Melaleuca quinquenervia, appears to be variably susceptible to this pathogen. Understanding the molecular basis of host resistance would enable better management of this rust disease. We identified resistant and susceptible individuals of M. quinquenervia and explored their differential gene expression in order to discover the molecular basis of resistance against A. psidii. Rust screening of germplasm showed a varying degree of response, with fully resistant to highly susceptible individuals. We used transcriptome profiling in samples collected before and at 5 days postinoculation (dpi). Differential gene expression analysis showed that numerous defense-related genes were induced in susceptible plants at 5 dpi. Mapping reads against the A. psidii genome showed that only susceptible plants contained fungal-derived transcripts. Resistant plants exhibited an overexpression of candidate A. psidii resistance-related genes such as receptor-like kinases, nucleotide-binding site leucine-rich repeat proteins, glutathione S-transferases, WRKY transcriptional regulators, and pathogenesis-related proteins. We identified large differences in the expression of defense-related genes among resistant individuals.

Efecto antimicrobiano de hojas de Melaleuca leucadendron L, que crece en la Ciénaga de Zapata / Antimicrobial effect of the leaves of Melaleuca leucadendron L growing in Cienaga de Zapata

Melaleuca leucadendron L es una planta comúnmente conocida como cayeput, que constituye una especie invasora y no deseada en la Ciénaga de Zapata, en la provincia de Matanzas. Por los usos que se refieren pudiera explotarse de forma razonable como antimicrobiano. Como objetivo, se pretendió determinar la actividad antimicrobiana en el extracto fluido obtenido de las hojas de la planta que crece silvestre en el mencionado territorio. El extracto se obtuvo mediante repercolación y el ensayo se realizó in vitro, utilizando los métodos de difusión en agar y dilución en medio líquido, enfrentando las diferentes concentraciones del extracto a bacterias, levadura y hongos filamentosos. Se demostró efecto microbicida del extracto para todos los microorganismos probados, estableciendo valores de concentración mínima inhibitoria, mínima bactericida y mínima fungicida; el efecto se mantuvo estable durante cuatro años. Estos resultados confirman el propósito de usar como antimicrobiano la materia prima vegetal en exceso disponible en la región. Se recomienda tener en cuenta lo discutido en el estudio en cuanto a los efectos indeseables, para lo que se requieren otros estudios que profundicen en tal sentido, y se observe la evaluación riesgo-beneficio a fin de usar la planta en la práctica médica con las precauciones que de igual forma demandan reconocidos antimicrobianos...(AU)

Melaleuca leucadendron L is a tree commonly known as cayeput, being an invasive, undesirable species in Cienaga de Zapata, in the province of Matanzas. According to the referred usages, it might be exploited in a reasonable way as an antimicrobial agent. As our objective we pretended to determine antimicrobial activity in the fluid extract of the leaves of this tree wildly growing in the before mentioned territory. The extract was obtained by repercolation and the assay was carried out in vitro, using the methods of diffusion in agar and dilution in a liquid media. Different concentrations of the extract were used against bacteria, yeast, and filamentous fungi. The microbicidal effect of the extract was demonstrated for all the tested microorganisms, establishing values of minimal inhibitory, minimal bactericidal and minimal fungicidal effects of the concentration. The effect kept steady during four years. These results confirm the purpose of using as antimicrobial the raw vegetable material existing in excess in the region. It is recommended to take into account the matters discussed in the study according to the undesirable effects, so other studies are required to deepen in that sense. The evaluation risk-benefit should be observed to use the tree in the medical practice with the precautions also demanded by other well-known antimicrobials...(AU)

Efecto antimicrobiano de hojas de Melaleuca leucadendron L, que crece en la Ciénaga de Zapata / Antimicrobial effect of the leaves of Melaleuca leucadendron L growing in Cienaga de Zapata

SUMARY Melaleuca leucadendron L is a tree commonly known as cayeput, being an invasive, undesirable species in Cienaga de Zapata, in the province of Matanzas. According to the referred usages, it might be exploited in a reasonable way as an antimicrobial agent. As our objective we pretended to determine antimicrobial activity in the fluid extract of the leaves of this tree wildly growing in the before mentioned territory. The extract was obtained by repercolation and the assay was carried out in vitro, using the methods of diffusion in agar and dilution in a liquid media. Different concentrations of the extract were used against bacteria, yeast, and filamentous fungi. The microbicidal effect of the extract was demonstrated for all the tested microorganisms, establishing values of minimal inhibitory, minimal bactericidal and minimal fungicidal effects of the concentration. The effect kept steady during four years. These results confirm the purpose of using as antimicrobial the raw vegetable material existing in excess in the region. It is recommended to take into account the matters discussed in the study according to the undesirable effects, so other studies are required to deepen in that sense. The evaluation risk-benefit should be observed to use the tree in the medical practice with the precautions also demanded by other well-known antimicrobials.

Carbon and nitrogen supply to the underground orchid, Rhizanthella gardneri.

*Rhizanthella gardneri is a rare and fully subterranean orchid that is presumably obligately mycoheterotrophic. R. gardneri is thought to be linked via a common mycorrhizal fungus to co-occurring autotrophic shrubs, but there is no experimental evidence to support this supposition. *We used compartmentalized microcosms to investigate the R. gardneri tripartite relationship. (13)CO(2) was applied to foliage of Melaleuca scalena plants and [(13)C-(15)N]glycine was fed to the common mycorrhizal fungus, and both sources traced to R. gardneri plants. *In our microcosm trial, up to 5% of carbon (C) fed as (13)CO(2) to the autotrophic shrub was transferred to R. gardneri. R. gardneri also readily acquired soil C and nitrogen (N), where up to 6.2% of C and 22.5% of N fed as labelled glycine to soil was transferred via the fungus to R. gardneri after 240 h. *Our study confirms that R. gardneri is mycoheterotrophic and acquires nutrients via mycorrhizal fungus connections from an ectomycorrhizal autotrophic shrub and directly from the soil via the same fungus. This connection with a specific fungus is key to explaining why R. gardneri occurs exclusively under certain Melaleuca species at a very limited number of sites in Western Australia.