Background: Paipa cheese is a traditional, semi-ripened cheese made from raw cow’s milk in Colombia. The aim of this work was to gain insights on the microbiota of Paipa cheese by using a culture-independent approach. Method: two batches of Paipa cheese from three formal producers were sampled during ripening for 28 days. Total DNA from the cheese samples was used to obtain 16S rRNA gene sequences by using Illumina technology. Results: Firmicutes was the main phylum found in the cheeses (relative abundances: 59.2–82.0%), followed by Proteobacteria, Actinobacteria and Bacteroidetes. Lactococcus was the main genus, but other lactic acid bacteria (Enterococcus, Leuconostoc and Streptococcus) were also detected. Stapylococcus was also relevant in some cheese samples. The most important Proteobacteria were Enterobacteriaceae, Aeromonadaceae and Moraxellaceae. Enterobacter and Enterobacteriaceae (others) were detected in all cheese samples. Serratia and Citrobacter were detected in some samples. Aeromonas and Acinetobacter were also relevant. Other minor genera detected were Marinomonas, Corynebacterium 1 and Chryseobacterium. The principal coordinates analysis suggested that there were producer-dependent differences in the microbiota of Paipa cheeses. Conclusions: lactic acid bacteria are the main bacterial group in Paipa cheeses. However, other bacterial groups, including spoilage bacteria, potentially toxin producers, and bacteria potentially pathogenic to humans and/or prone to carry antimicrobial resistance genes are also relevant in the cheeses.

S- and Fe-cycling bacteria can decisively affect the crystallization of Fe-bearing minerals in sediments from fluvial environments. We have studied the relationships between the Fe-bearing mineral assemblage and the bacterial community composition in the sediments rich in organic matter from the upper Chicamocha river basin (Colombia). Rapid flowing sections of the river contain sediments that have a high redox potential, are poor in organic matter and are enriched in kaolinite and quartz. On the other hand, the mineral assemblage of the sediments deposited in the La Playa dam with a high content in organic matter is enriched in Fe-bearing minerals: (a) vivianite and pyrite in the permanently flooded sediments of the dam and (b) pyrite and goethite in the periodically emerged sediments. The bacterial community composition of these sediments reveals anthropic organic matter pollution processes and biodegradation associated with eutrophication. Moreover, periodically emerged sediments in the La Playa dam contain bacterial groups adapted to the alternation of dry and wet periods under oxic or anoxic conditions. Cell-shaped aggregates with a pyritic composition suggest that sulfate-reducing bacteria (SRB) communities were involved in the precipitation of Fe-sulfides. The precipitation of vivianite in the flooded sediments was favored by a greater availability of Fe(II), which promoted the iron-reducing bacteria (IRB) enrichment of the sediments. The presence of sulfur-oxidizing bacteria (SOB) in the flooded sediments and the activity of iron-oxidizing bacteria (IOB) in the periodically emerged sediments favored both pyrite crystallization under a high sulfide availability and the oxidation of microbially precipitated monosulfides. Moreover, IOB enhanced goethite formation in the periodically emerged sediments.

The sludge produced in wastewater treatment plants constitutes a potential alternative to replace traditional fertilizers and reduce costs in agricultural activities. The objective of this work was to compare the fertilizing effect of the sludge produced in the wastewater treatment plant of Sotaquirá-Colombia, with the fertilizers traditionally used on the tomato crop (Solanum lycopersicum L). For this, the sludge was previously stabilized with two different treatments: dehydration and the addition of CaO. Subsequently, four treatments were applied to the tomato seedlings, 135 g.kg-1 of dehydrated biosolid, 135 g.kg-1 biosolid stabilized with CaO, 135 g.kg-1 of ABIMGRA®, 135 g.kg-1 of naturcomplet®-G, and greenhouse soil without biosolids. The height of the plant, the fresh and dry mass, foliar area, and fruits per plant, were measured at 0, 30, 60 and 90 days after sowing. In tomato fruits, the concentrations of heavy metals, coliforms, helminth eggs, somatic phages, and Salmonella sp., were determined. The dehydrated biosolids had a significant effect on the size, the fresh mass, foliar area, and the number of fruits per plant, compared to the alkaline biosolids. The dry mass of the plants (120 g. plant-1) was similar to traditional fertilizers and biosolids. Tomatoes produced with biosolids had low levels of heavy metals and an absence of pathogenic microorganisms. In conclusion, the biosolid obtained by dehydration in Sotaquirá can be used as a potential fertilizer in tomato cultivation.