Methane and carbon dioxide flux in the profile of wood ant (Formica aquilonia) nests and the surrounding forest floor during a laboratory incubation.

We compared methane (CH4) and carbon dioxide (CO2) fluxes in samples collected from the aboveground parts of wood ant nests and in the organic and mineral layer of the surrounding forest floor. Gas fluxes were measured during a laboratory incubation, and microbial properties (abundance of fungi, bacteria and methanotrophic bacteria) and nutrient contents (total and available carbon and nitrogen) were also determined. Both CO2 and CH4 were produced from ant nest samples, indicating that the aboveground parts of wood ant nests act as sources of both gases; in comparison, the forest floor produced about four times less CO2 and consumed rather than produced CH4 Fluxes of CH4 and CO2 were positively correlated with contents of available carbon and nitrogen. The methanotrophic community was represented by type II methanotrophic bacteria, but their abundance did not explain CH4 flux. Fungal abundance was greater in ant nest samples than in forest floor samples, but bacterial abundance was similar in both kinds of samples, suggesting that the organic materials in the nests may have been too recalcitrant for bacteria to decompose. The results indicate that the aboveground parts of wood ant nests are hot spots of CO2 and CH4 production in the forest floor.

Microbiology of healing mud (fango) from Roman thermae aquae iasae archaeological site (Varazdinske Toplice, Croatia).

We found well-preserved, rocky artefacts that had been buried in the healing mud (fango) for more than 1,500 years at the Roman archaeological site at Varazdinske Toplice. This Roman pool with fango sediments and artefacts is fed from hot sulphidic springs. The fango exhibited nearly neutral pH, a high level of organic C, an elevated concentration of heavy metals and a high total microbial biomass, greater than 10(8) cells per gram of dry weight. The dominant microbes, assessed by molecular profiling (denaturing gradient gel electrophoresis), were affiliated with Thiobacillus, Sulfuricurvum, Polaromonas, and Bdellovibrio. Polymerase chain reaction screening for microbial functional guilds revealed the presence of sulphur oxidizers and methanogens but no sulphate reducers. The dominance of four Proteobacterial classes (α-, ß-, δ- and ε-Proteobacteria) was confirmed by fluorescence in situ hybridisation; Actinobacteria were less abundant. Cultivable bacteria represented up to 23.4 % of the total bacterial counts when cultivation media was enriched with fango. These bacteria represented the genera Acinetobacter, Aeromonas, Arthrobacter, Comamonas, Ewingella, Flavobacterium, Pseudomonas, Rahnella and Staphylococcus. This study showed that the heterogeneous nature of fango at neutral pH created various microniches, which largely supported microbial life based on sulphur-driven, autotrophic denitrification.