The complete genome sequence of Geobacillus thermodenitrificans NG80-2, a thermophilic bacillus isolated from a deep oil reservoir in Northern China, consists of a 3,550,319-bp chromosome and a 57,693-bp plasmid. The genome reveals that NG80-2 is well equipped for adaptation into a wide variety of environmental niches, including oil reservoirs, by possessing genes for utilization of a broad range of energy sources, genes encoding various transporters for efficient nutrient uptake and detoxification, and genes for a flexible respiration system including an aerobic branch comprising five terminal oxidases and an anaerobic branch comprising a complete denitrification pathway for quick response to dissolved oxygen fluctuation. The identification of a nitrous oxide reductase gene has not been previously described in Gram-positive bacteria. The proteome further reveals the presence of a long-chain alkane degradation pathway; and the function of the key enzyme in the pathway, the long-chain alkane monooxygenase LadA, is confirmed by in vivo and in vitro experiments. The thermophilic soluble monomeric LadA is an ideal candidate for treatment of environmental oil pollutions and biosynthesis of complex molecules.

Xylose is a major component of lignocellulose and the second most abundant sugar present in nature. Efficient utilization of xylose is required for the development of economically viable processes to produce biofuels and chemicals from biomass. However, there are still some bottlenecks in the bioconversion of xylose, including the fact that some microorganisms cannot assimilate xylose naturally and that the uptake and metabolism of xylose are inhibited by glucose, which is usually present with xylose in lignocellulose hydrolysate. To overcome these issues, numerous efforts have been made to discover, characterize, and engineer the transporters and enzymes involved in xylose utilization to relieve glucose inhibition and to develop recombinant microorganisms to produce fuels and chemicals from xylose. Here we describe a recent advancement focusing on xylose-utilizing pathways, biosynthesis of chemicals from xylose, and engineering strategies used to improve the conversion efficiency of xylose.

The ability to grow at moderate acidic conditions (pH 4.0–5.0) is important toEscherichia colicolonization of the host’s intestine. Several regulatory systems are known to control acid resistance inE. coli, enabling the bacteria to survive under acidic conditions without growth. Here, we characterize an acid-tolerance response (ATR) system and its regulatory circuit, required forE. coliexponential growth at pH 4.2. A two-component system CpxRA directly senses acidification through protonation of CpxA periplasmic histidine residues, and upregulates thefabAandfabBgenes, leading to increased production of unsaturated fatty acids. Changes in lipid composition decrease membrane fluidity, F₀F₁-ATPase activity, and improve intracellular pH homeostasis. The ATR system is important forE. colisurvival in the mouse intestine and for production of higher level of 3-hydroxypropionate during fermentation. Furthermore, this ATR system appears to be conserved in other Gram-negative bacteria.

The depleting petroleum reserve, increasingly severe energy crisis, and global climate change are reigniting enthusiasm for seeking sustainable technologies to replace petroleum as a source of fuel and chemicals. In this paper, the efficiency of the MVA pathway on isoprene production has been improved as follows: firstly, in order to increase MVA production, the source of the “upper pathway” which contains HMG-CoA synthase, acetyl-CoA acetyltransferase and HMG-CoA reductase to covert acetyl-CoA into MVA has been changed from Saccharomyces cerevisiae to Enterococcus faecalis; secondly, to further enhance the production of MVA and isoprene, a alanine 110 of the mvaS gene has been mutated to a glycine. The final genetic strain YJM25 containing the optimized MVA pathway and isoprene synthase from Populus alba can accumulate isoprene up to 6.3 g/L after 40 h of fed-batch cultivation.