Biochemistry and Genetics of Bacterial Bioluminescence

Bacterial light production involves enzymes-luciferase, fatty acid reductase, and flavin reductase-and substrates-reduced flavin mononucleotide and long-chain fatty aldehyde-that are specific to bioluminescence in bacteria. The bacterial genes coding for these enzymes, luxA and luxB for the subunits of luciferase; luxC, luxD, and luxE for the components of the fatty acid reductase; and luxG for flavin reductase, are found as an operon in light-emitting bacteria, with the gene order, luxCDABEG. Over 30 species of marine and terrestrial bacteria, which cluster phylogenetically in Aliivibrio, Photobacterium, and Vibrio (Vibrionaceae), Shewanella (Shewanellaceae), and Photorhabdus (Enterobacteriaceae), carry lux operon genes. The luminescence operons of some of these bacteria also contain genes involved in the synthesis of riboflavin, ribEBHA, and in some species, regulatory genes luxI and luxR are associated with the lux operon. In well-studied cases, lux genes are coordinately expressed in a population density-responsive, self-inducing manner called quorum sensing. The evolutionary origins and physiological function of bioluminescence in bacteria are not well understood but are thought to relate to utilization of oxygen as a substrate in the luminescence reaction

Impact of Tillage Methods on Environment, Energy and Economy

ISSN 2210-4410, eISBN 9783319990767Soil tillage involves the mechanical manipulation of soils used for crop production. Tillage is done to prepare an optimal seedbed, to loosen compacted soil layers, to control weeds, to increase aeration, to incorporate plant residues into the soil, to facilitate water infiltration and soil moisture storage, and to control soil temperature. Nonetheless, soil tillage is one of the highest energy-consuming, environment-polluting and expensive technological processes in agriculture. Conventional tillage with ploughing is the most widely used practice. Conventional tillage has low efficiency, requires high-powered tractors with high fuel consumption and greenhouse gases emissions. Moreover, the cost of conventional tillage is high, and the influence on the soil structure, degradation, leaching of nutrients and the most fertile soil is negative. Here we review the impact of tillage methods on soil quality, environment and economy. Due to the disadvantages of conventional tillage, sustainable tillage area increases each year by 4-6 million ha worldwide. Under sustainable tillage such as minimal or no-tillage, the total soil surface modified by the wheels of agricultural machinery is 20-40% lower than for conventional tillage. Sustainable tillage preserves better soil physical properties and biological processes. A comparison of tillage methods show that no-tillage has the highest energy efficiency ratio of 14.0, versus 12.4 for deep ploughing. The most expensive tillage operation is deep ploughing. The use of agricultural machinery under sustainable tillage conditions and preparation of soils without using a plough can reduce costs from 25% to 41%, compared with conventional tillageVytauto Didžiojo universitetasŽemės ūkio akademij