Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 21

Liczba wyników na stronie
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 2 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników

Wyniki wyszukiwania

help Sortuj według:

help Ogranicz wyniki do:
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 2 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
Signature lipid biomarker (SLB) analysis is a useful tool for identifying microorganisms and character­izing microbial communities in natural systems. Specific fatty acids, especially phospholipids (PLFA), are es­sential membrane components, make up a relatively constant proportion of the microorganisms under natural conditions and their patterns provide insight into the bacterial and fungal community structure and biomass. This method is based on direct extraction of fatty acids from cultured bacteria or environmental samples and determining the isolated methyl ester fatty acids (FAME) using gas chromatography (GC). Several PLFAs are useful markers for the detection of the specific groups, and whole cell fatty acid analysis is used for routine identification of microbial species. The fatty acid analysis has been successfully applied for the characteriza­tion of microbial communities from agricultural soils, from sites contaminated with heavy metals, aromatic compounds, alkaline dust, acid rain and from other diverse habitats.
Many polycyclic aromatic hydrocarbons (PAHs) are known to be toxic and carcinogenic for humans, and their contamination of soils and aquifers is of great environmental concern. Some microorganisms, mainly from the genera Pseudomonas and Mycobacterium, were found to be capable of transforming and degrading PAHs. These abilities may be useful in removal of PAHs from the environment. The successful application of bacteria to the bioremediation of PAH-contaminated sites requires a deeper understanding of how microbial PAH degradation proceeds. In this review, the bacteria involved and the metabolic pathways for the degradation of many PAHs are summarized and the biological aspects of PAH bioremediation are discussed.
The aim of this study was to evaluate the impact of catechol and phenol added to culture media separately and with glucose as an additional, easily-degradable carbon source on fatty acid methyl ester (FAME) composition in Pseudomonas vesicularis. Simultaneously, the degradation rates of aromatic substrates used were investigated in single and binary substrate systems. Both catechol and phenol treatments caused changes in the distribution of tested groups of fatty acids. The most noticeable changes included an increase in degree of fatty acid saturation, the appearance of branched and disappearance of hydroxy fatty acids as compared to the control sample with glucose. Under catechol or phenol treatment sat/unsat ratio showed the values of 8.63 and 11.38, respectively, whereas in control cells it reached the value of 2.66. The high level of saturation comes from the high content of cyclopropane fatty acids in bacteria under exposure to aromatic substrates, regardless of the presence of glucose. In these treatments their content was more than 3-fold higher compared to the control. It has been demonstrated that glucose supplementation of culture media containing single aromatic substrate extended the degradation rates of catechol and phenol by P. vesicularis, caused an increase in number of cells but did not significantly change the fatty acid profiles in comparison with bacteria growing on catechol and phenol added to the media individually.
Changes in cellular fatty acid composition during naphthalene degradation, at the concentrations of 0.5 g l⁻¹ or 1.0 g l⁻¹, by Pseudomonas sp. JS150 were investigated. In response to naphthalene exposure an increase in saturated/unsaturated ratio was observed. Additionally, the dynamic changes involved alterations in the contents of hydroxy, cyclopropane and branched fatty acids. Among the classes of fatty acids tested the most noticeable changes in the abundance of cyclopropane fatty acids were observed. Since day 4 of incubation these fatty acids were not dectected in bacterial cells growing on naphthalene. In contrast, markedly increased in the percentage of hydroxy fatty acids over time was observed. However, the proportions of saturated straight-chain and branched fatty acids did not change such significantly.
Bacteria can adapt to various environmental factors such as temperature, pressure, ions, nutrients and toxic substances by modifying their membranes to maintain them in a fluid state. These modifications within the cytoplasmatic membrane particularly result from changes in the fatty acid composition and interaction between proteins and lipids. Fatty acids, mainly phospholipid fatty acids, play a role as a good biomarker of changes of physiological status of microorganisms caused by external factors. A greater understanding of the detailed physiological mechanisms of bacterial membrane lipid adaptation, especially to toxic substances and solvents, are important for researchers who use bacteria in bioremediation and biotransformation processes.
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 2 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.