Gelsa Edith Englert

Analysis of Salt-Containing Biofilms on Limestone Buildings of the Mayan Culture at Edzna, Mexico

Biofilms on the salted ceiling of a limestone tunnel at the Mayan site of Edzna, Mexico, were characterised using SEM, EDS, chemical analysis, light microscopy, culture and pigment analysis. Major superficial biomass was pigmented, scytonemin-rich Subsection II cyanobacteria. Main endolithic phototrophs were Subsection I and II cyanobacteria and the alga Nanochlorum. Bacteria and actinomycetes of the Geodermatophilus, nocardioform, and streptomycete groups were present at all levels. Salt crystals, mainly sulfates, were found throughout the stone. Microbial ion transport, metabolite production, chelation, and water retention caused degradation and salt deposits. Exfoliation is the major erosion process.

Nanobacteria-like particles: a threat to cell cultures

The main goal of this study is to alert researchers who work with cell cultures for the risk of contamination by structures called nanobacteria (NB). NB are tiny structures with size varying from 80 to 500 nm, commonly occurring in clusters and producing a biofilm which contains carbonate or hydroxyl apatite. The most likely source of cell culture contamination by such organisms is serum used as supplement in culture media. The presence of NB leads to a progressive culture deterioration with accumulation of granules (probably phagocytized NB) in cytoplasmic vacuoles, an increasing number of dead cells in the supernatant and degeneration of cells that remained attached to the bottom of the vessel. NB can also be found in culture supernatants where they are found in clusters with variable size and displaying brownian movement. In this study, 19 cell lineages, 8 batches of sera and 1 batch of growth supplement from different sources were analyzed. Samples from sera were cultured in Eagle’s Minimum Essential Medium (E-MEM) or incubated directly at 37oC. Tests carried out to detect the presence of extracellular bacteria, Mycoplasma sp and viruses were all negative. Analysis by scanning electron microscopy (SEM) revealed tiny oval structures less than 500 nm in size, isolated or in small groups, in all material analyzed except in one fetal bovine serum batch.

The corrosion behaviour of mild steel and type 304 stainless steel in media from an anaerobic biodigestor

Abstract Mild steel and AISI 304 stainless steel samples were exposed to the aqueous solutions from an anaerobic biodigestor of wastewater, showing quite different behaviours. Carbon steel presented generalized corrosion whereas stainless steel, as-received or sensitized, tended to show some localized corrosion. Both materials presented bacteria attachment, particularly sulphate reducing bacteria (SRB), forming biofilms which were abundant and mixed with corrosion products on the mild steel surface and thin and patchy on stainless steel surfaces. Different types of anaerobic and aerobic bacteria were detected in the medium. Experiments were carried out both at 1 and at 7 atmospheres pressure, in presence of a gaseous phase containing N 2 , CO 2 and CH 4 . Potentiodynamic experiments were conducted in order to have a better insight on the electrochemical behaviour of the material in this medium.

Aderência bacteriana in vitro a lentes intra-oculares de polimetilmetacrilato e de silicone

PURPOSE: To evaluate bacterial adherence to silicone and polymetylmethacrylate (PMMA) intraocular lenses as a risk factor for postsurgery endophthalmitis by using an in vitro model with three potentially pathogenic microorganisms. METHODS: In vitro experiments were carried out with the Staphylococcus aureus ATCC 29213, Staphylococcus epidermidis (clinical isolate) and Pseudomonas aeruginosa ATCC 27853 strains including growth curves, tests to verify capsule production, hydrophobicity and adherence to different materials as well as optical microscopy, scanning electronic microscopy (SEM) and atomic force microscopy (AFM). RESULTS: No relation between capsule production, adherence of the strains tested and amount of microorganisms was observed; no statistically significant differences were detected between S. aureus and S. epidermidis adherence to polymetylmethacrylate and silicone intraocular lenses; P. aeruginosa was the most adherent microorganism to both materials. This adherence pattern was confirmed by SEM, while biofilm production by the three strains was visualized by AFM. CONCLUSIONS: In vitro experiments showed no differences of bacterial adherence between PMMA and silicone lenses, but P. aeruginosa displayed a greater level of adherence in relation to staphylococci. All three strains were shown to produce biofilm. Silicone was shown to be more hydrophobic when compared to polymethylmethacrylate.

Physical and Microbiological Analysis of Sandstone Deterioration in the Argentine Jesuit Missions

ABSTRACT Mainly cyanobacteria, but also algae and fungi, were identified on the Jesuit missions San Ignacio Miní, Loreto, Santa María and Santa Ana, in NE Argentina. Many organisms were deeply pigmented, indicative of stressful conditions. San Ignacio samples of itacurú rock showed higher colonization and biodiversity, related to higher porosity allowing entry of water and nutrients. Sandstone from other locations was arenitous, containing 95% silicates. Physicochemical analyses suggested mobilization of ions, particularly Fe, from within the stone to the surface. This intense deteriorating colonization, together with climatic weathering, transforms the sandstone to a “protosoil,” for growth of bryophytes and higher plants.