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Contribution of culture-independent methods to cave aerobiology: The case of Lascaux Cave
Published in Cesareo Saiz-Jimenez, The Conservation of Subterranean Cultural Heritage, 2014
P.M. Martin-Sanchez, C. Saiz-Jimenez
Pseudomonas, with the 65.1% of clones, was the most abundant genus of Gammaproteo-bacteria, mainly represented by two species, P. azotoformans (49.4%) and P. stutzeri (14.5%). In spite of the abundance of P. azotoformans in this clone library, no strain of this species could be isolated by culturing. A strain of P. azotoformans, isolated from rice soil exposed to cyhalofop-butyl for many years, was able to degrade this herbicide in the laboratory (Nie et al. 2011). The species P. stutzeri, which was also detected by culture-dependent methods (Table 1), is ubiquitous in the environment, occupying diverse ecological niches, and has been described as an opportunistic pathogen for humans. Pseudomonas stutzeri has a high degree of physiological and genetic adaptability. Like other Pseudomonas species, P. stutzeri is involved in environmentally important metabolic activities related to metal cycling and degradation of biogenic and xenobiotic compounds (oil derivatives, aromatic and non-aromatic hydrocarbons and biocides (Lalucat el al. 2006).
Plant mediated synthesis of AgNPs and its applications: an overview
Published in Inorganic and Nano-Metal Chemistry, 2021
Aswathi Shyam, Smitha Chandran S., Bini George, Sreelekha E.
Nanoparticle synthesis arises due to the resistance of the bacterial cell to the environmental silver ions.[13] The silver resistant bacteria strain Pseudomonas stutzeri AG259 can deposit AgNPs with size range 35–46 nm along with some Ag2S, in the cell. To overcome the toxic effect of metal ions, a mechanism of defence that involves the reduction of ions or water insoluble complex formation is developed by the bacteria.[14] Even though some studies have shown different results, it is commonly believed that enzymes present in the organisms illustrate an important role in the reduction processes. The dried cells of Lactobacillus sp.A09 and Bacillus megaterium D01 are able to reduce silver ions through a non-enzymatic bioreduction process. Unlike other cases, here the reduction of silver ions is achieved by the interaction of ions with the groups present on the cell wall of the microorganisms. The most commonly accepted procedure for the biosynthesis of AgNPs is the conversion from nitrate to nitrite with the help of enzyme nitrate reductase.
Understanding human health risks caused by antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARG) in water environments: Current knowledge and questions to be answered
Published in Critical Reviews in Environmental Science and Technology, 2020
Mohan Amarasiri, Daisuke Sano, Satoru Suzuki
In the transformation process, bacteria will uptake and integrate the extracellular DNA present in the environment (Thomas & Nielsen, 2005). Environmental ARG pool is formed under grazing pressure by protists, which is found to be constant (Bien, Thao, Kitamura, Obayashi, & Suzuki, 2017). A large number of naturally transformable prokaryotes in the environment have been reported (de Vries & Wackernagel, 2005; Johnsborg, Eldholm, & Håvarstein, 2007; Lorenz & Wackernagel, 1994). Natural transformation of Pseudomonas stutzeri strains isolated from soil and marine sediments to rifampicin resistance by chromosomal DNA have been observed (Stewart & Sinigalliano, 1991). Transformation of naturally competent Acinetobacter calcoaceticus by plasmid and chromosomal DNA adsorbed on sand and ground water/ground water aquifer microcosms was observed; chromosomal DNA transformation frequency was 103-104 times higher than plasmid DNA transformation frequency (Chamier, Lorenz, & Wackernagel, 1993). Transformation of environmental bacteria found in other aquatic environments like river water, spring water and groundwater have also been reported (Davison, 1999).
Co-biodegradation studies of naphthalene and phenanthrene using bacterial consortium
Published in Journal of Environmental Science and Health, Part A, 2020
The above results and degradation rates can be compared with previous studies carried out on degradation of PAHs. Hesham et al.[33] conducted a study where they identified a yeast (AH70) which was isolated from oil-polluted soils being able to utilize naphthalene at the rate of 89.76% and phenanthrene at the rate of 77.21%, pyrene in 10 days. Sadighbayan et al.[34] isolated bacteria that were able to degrade a mixture of PAHs and the degradation efficiency was found to be 57.1% for naphthalene and 82.1% for phenanthrene in 7 days. Up to 82.1% of PAH degradation was achieved at a concentration of 1000 mg/L by 14 types of bacteria. Janbandhu et al.[35] isolated a bacterial strain Pseudomonas stutzeri ZP2 from soil in oil refinery fields in China. They reported that the strain can reduce about 96% phenanthrene at a concentration of 250 mg/L within 6 days. In a study conducted by Jiang et al.,[36] they isolated a phenanthrene-degrading Pseudomonas sp. strain which was named as Pseudomonas sp. LZ-Q. This isolate was able to degrade 92.27% of phenanthrene at a concentration of 1000 mg/L in 5 days and was able to degrade 96% of 20 mg/L phenanthrene within 60 days in a membrane bioreactor at continuous mode. Mnif et al.,[37] developed a bacterial consortium PHMM, composed of Staphylococcus arlettae and Pseudomonas aeruginosa, which degraded phenanthrene at a concentration of 200 mg/L and 500 mg/L in 10 days.