Search results for "Bacteria"
showing 10 items of 4919 documents
Excitation Energy Transfer in Isolated Chlorosomes from Chlorobaculum tepidum and Prosthecochloris aestuarii
2012
Excitation energy transfer in chlorosomes from photosynthetic green sulfur bacteria, Chlorobaculum (Cba.) tepidum and Prosthecochloris (Pst.) aestuarii, have been studied at room temperature by time-resolved femtosecond transient absorption spectroscopy. Bleach rise times from 117 to 270 fs resolved for both chlorosomes reflect extremely efficient intrachlorosomal energy transfer. Bleach relaxation times, from 1 to 3 ps and 25 to 35 ps, probed at 758 nm were tentatively assigned to intrachlorosomal energy transfer based on amplitude changes of the global fits and model calculations. The anisotropy decay constant of about 1 ps resolved at 807 nm probe wavelength for the chlorosomes from Chlo…
Extraction of Enzymes from Tissues, Cells and Cell-Organelles
1994
Microorganisms, such as bacteria, algae, moulds and others, are ruptured by sonication, by passage through a French press [1, 2] (Fig. 2.1) or a Manton-Gaulin homogenizer [3], by blending with glass beads [4], or by digesting the cell walls enzymically [5]. Extract preparation is preferably performed in the cold (+4 °C).
Real time analysis of Escherichia coli biofilms using calorimetry
2008
Abstract Microbial communities grow more stably when they are associated to surfaces or organized in aggregates. This advantage of biofilms is technically exploited for the degradation of xenobiotics or in biocatalysis, where the fixed biomass has the added advantage of easier separation of excreted products. Whereas the biothermodynamic analysis of growth and product formation of suspended cells is developing fast, there are only few reports on the calorimetric analysis and biothermodynamic interpretation of biofilm evolution. Experiments illustrate the ability of calorimetry to monitor the physiological state of biofilms in real time. Sessile cells of Escherichia coli DH5α DSM 6897 were s…
Inhibition of bacterial virulence factors of foodborne pathogens by paprika (Capsicum annuum L.) extracts
2022
Abstract Capsicum annuum extracts of different polarities were tested for their antimicrobial, antibiofilm, and anti-Quorum sensing (QS) activity against several pathogenic microorganisms and possible toxic effects using an in vivo model (Galleria mellonella L.). Hexane (HE) and Chloroform extract (CE) were the most active in inhibiting biofilm formation of the eight bacteria tested, with inhibition percentages between 22 and 88% for a concentration of 100 μg/mL. These extracts were potent inhibitors of Staphylococcus aureus biofilm, and microscopy analysis confirmed a significant reduction in adhered cells. Moreover, polystyrene surfaces coated with these extracts decreased Staph. aureus a…
The complex life-cycle of a polymorphic prokaryote epibiont of the photosynthetic bacterium Chromatium weissei
1993
In natural populations of the anaerobic phototrophic bacterium Chromatium weissei, many cells support a prokaryotic epibiont. This epibiont appears in several forms, all from the life cycle of a single species. A typical epibiont consists of one to five flattened coccoid cells stacked one above the other, perpendicular to the C. weissei surface. The cells at the proximal and distal ends of the stack are 0.6 μm in diameter and 0.8 μm in length; mid-stack cells are slightly shorter. A typical three or four cell stack is 2 μm in length. Small mesosome-like inclusions in the distal cell are involved in the development of ‘droplet’ shaped cells which are released from the end of each stack. Thes…
Photoinduced DNA Lesions in Dormant Bacteria. The Peculiar Route Leading to Spore Photoproduct Unraveled by Multiscale Molecular Dynamics
2020
Some bacterial species enter a dormant state in the form of spores to resist to unfavorable external conditions. Spores are resistant to a wide series of stress agents, including UV radiation, and can last for tens to hundreds of years. Due to the suspension of biological functions such as DNA repair, they accumulate DNA damage upon exposure to UV radiation. Differently from active organisms, the most common DNA photoproduct in spores are not cyclobutane pyrimidine dimers, but rather the so-called spore photoproduct. This non-canonical photochemistry results from the dry state of DNA and the binding to small acid soluble proteins that drastically modify the structure and photoreactivity of …
Biotic methylation of mercury by intestinal and sulfate-reducing bacteria and their potential role in mercury accumulation in the tissue of the soil-…
2014
Abstract Monomethylmercury as one of the most toxic mercury species influences the health and development of higher organisms and tends to accumulate in the tissue of animals and humans. The aim of this study was to explore the mercury methylating capability of (1) intestinal microbiota of the soil-living earthworm Eisenia foetida (E. foetida) and (2) intestinal sulfate reducing-bacteria in pure cultures. After exposing animals to inorganic mercury chloride (4 mg kg−1 Hg2+) in soil and sterile soil for ten days, the amount of methylmercury in tissue was measured. Despite sterilization of soil, the accumulation of the organic mercury species in tissue was 51 ng g−1. To elucidate the potentia…
Bacteria of the Genus Roseobacter Associated with the Toxic Dinoflagellate Prorocentrum lima
1998
The dinoflagellate Prorocentrum lima is known to produce diarrhetic shellfish poisons. However, it is yet unclear if the dinoflagellates themselves or the bacteria associated with them produce the toxins. Here we analyze the toxicity as well as the spectrum of bacteria in two cultures of P. lima, namely P. lima-SY and P. lima-ST, which initially derived from the same P. lima strain PL2V. Toxicity tests, applying the Artemia bioassay revealed in both cultures high levels of toxins. The bacteria, associated with the two cultures, were identified by PCR/nucleotide sequence analysis of the 16S rRNA gene. From cultures of P. lima-SY the dominant sequence was found to share a 93.7% similarity wit…
Insecticidal Activity of Strains of Bacillus thuringiensis on Larvae and Adults of Bactrocera oleae Gmelin (Dipt. Tephritidae)
1999
The olive fly, Bactrocera oleae, is the key pest on olives in the Mediterranean area. The pest can destroy, in some cases, up to 70% of the olive production. Its control relies mainly on chemical treatments, sometimes applied by aircraft over vast areas, with their subsequent ecological and toxicological side effects. Bacillus thuringiensis is a spore-forming soil bacterium which produces a protein crystal toxic to some insects, including the orders of Lepidoptera, Diptera, and Coleoptera and other invertebrates. The aim of this study was to search for isolates toxic to B. oleae. Several hundred B. thuringiensis isolates were obtained from olive groves and olive presses in different areas o…