Global climate change has stimulated efforts to reduce CO(2) emissions. One approach to addressing this problem is to recycle CO(2) directly into fuels or chemicals using photosynthesis. Here we genetically engineered Synechococcus elongatus PCC7942 to produce isobutyraldehyde and isobutanol directly from CO(2) and increased productivity by overexpression of ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco). Isobutyraldehyde is a precursor for the synthesis of other chemicals, and isobutanol can be used as a gasoline substitute. The high vapor pressure of isobutyraldehyde allows in situ product recovery and reduces product toxicity. The engineered strain remained active for 8 d and produced isobutyraldehyde at a higher rate than those reported for ethanol, hydrogen or lipid production by cyanobacteria or algae. These results underscore the promise of direct bioconversion of CO(2) into fuels and chemicals, which bypasses the need for deconstruction of biomass.

An engineered microbe transforms carbon dioxide into a prospective liquid fuel in tandem with electrical power rather than light.

No abstract

Producing biofuels directly from cellulose, known as consolidated bioprocessing, is believed to reduce costs substantially compared to a process in which cellulose degradation and fermentation to fuel are accomplished in separate steps. Here we present a metabolic engineering example for the development of a Clostridium cellulolyticum strain for isobutanol synthesis directly from cellulose. This strategy exploits the host's natural cellulolytic activity and the amino acid biosynthesis pathway and diverts its 2-keto acid intermediates toward alcohol synthesis. Specifically, we have demonstrated the first production of isobutanol to approximately 660 mg/liter from crystalline cellulose by using this microorganism.

SummarySalmonella entry into epithelial host cells results from the host actin cytoskeleton reorganization that is induced by a group of bacterial proteins delivered to the host cells by the Salmonella type III secretion system. SopE, SopE2 and SopB activate CDC42 and Rac1 to intercept the signal transduction pathways involved in actin cytoskeleton rearrangements. SipA and SipC directly bind actin to modulate the actin dynamics facilitating bacterial entry. Biochemical studies have indicated that SipA decreases the critical concentration for actin polymerization and may be involved in promoting the initial actin polymerization in Salmonella-induced actin reorganization. In this report, we conducted experiments to analyze the in vivo function(s) of SipA during Salmonella invasion. SipA was found to be preferentially associated with peripheral cortical actin filaments but not stress fibres using permeabilized epithelial cells. When polarized Caco-2 cells were infected with Salmonella, actin cytoskeleton rearrangements induced by the wild-type strain had many filopodia structures that were intimately associated with the bacteria. In contrast, ruffles induced by the sipA null mutant were smoother and distant from the bacteria. We also found that the F-actin content in cells infected with the sipA mutant decreased nearly 80% as compared to uninfected cells or those infected with the wild-type Salmonella strain. Furthermore, expression of either the full-length or the SipA 459-684 actin-binding fragment induced prominent punctuate actin assembly in the cortical region of COS-1 cells. These results indicate that SipA is involved in modulating actin dynamics in cultured epithelial cells during Salmonella invasion.

Salmonella translocate bacterial effectors into host cells to confer bacterial entry and survival. It is not known how the host cells cope with the influx of these effectors. We report here that the Salmonella effector, SopA, interacts with host HsRMA1, a ubiquitin E3 ligase with a previously unknown function. SopA is ubiquitinated and degraded by the HsRMA1-mediated ubiquitination pathway. A sopA mutant escapes out of the Salmonella-containing vacuoles less frequently to the cytosol than wild type Salmonella in HeLa cells in a HsRMA1-dependent manner. Our data suggest that efficient bacterial escape into the cytosol of epithelial cells requires HsRMA1-mediated SopA ubiquitination and contributes to Salmonella-induced enteropathogenicity.Pathogenic Salmonella cause food poisoning, gastrointestinal inflammation, typhoid fever, and septicemia in humans. Salmonella enterica serovar typhimurium (S. typhimurium) encodes two Type III secretion systems within the Salmonella pathogenicity islands 1 and 2 (SPI-1 3 and SPI-2) that are required for Salmonella entry and subsequent survival inside the host, respectively (1-5). Among the secreted proteins in SPI-1, SipA, SipC, SopE, SopE2, and SopB (also known as SigD) were found to be responsible for promoting bacterial entry by modulating the host actin cytoskeleton (6 -11). SPI-2 effectors are responsible for subsequent Salmonella survival inside the host cells by modulating bacterial trafficking (12-16). In addition, SPI-1 effectors SipA, SopA, SopB, SopD, SopE, and SopE2 are largely responsible for inducing inflammation and diarrhea in animal models (17-19) through yet undefined mechanisms.Ubiquitination is the main protein degradation pathway that governs a variety of cellular processes including cell cycle, vesicle trafficking, and signal transduction (20). Ubiquitination involves a multienzyme cascade consisting of classes of enzymes known as E1 (ubiquitin-activating enzyme), E2 (ubiquitin-conjugating enzyme), and E3 (ubiquitin protein ligase) (20). Ubiquitinated proteins are either rapidly degraded by the 26 S proteasome (21) or targeted to various specific cellular compartments (20,22). The ubiquitin ligases (E3) play pivotal roles in defining the specificity of proteins targeted for ubiquitination.HsRMA1 (RING finger protein with membrane anchor, also named RNF5) is a newly identified membrane-bound ubiquitin E3 ligase belonging to the novel RING finger protein family (23-26). HsRMA1 is well conserved in higher eukaryotes but not present in the yeast genome. It has been reported that Arabidopsis thaliana AtRMA1 is able to complement the yeast temperature-sensitive, secretion-deficient sec15 mutation (23). One of the late-acting sec genes is sec15, which is involved in the vesicle trafficking from the Golgi to the plasma membrane (27, 28). Recently, HsRMA1 was reported to interact with paxillin to alter the localization of paxillin to regulate cell motility (29). The importance of ubiquitination in the secretory pathway and endocytosis has also been described (20). ...

The SARS-CoV-2 variants replacing the first wave strain pose an increased threat by their potential ability to escape pre-existing humoral protection. An angiotensin converting enzyme 2 (ACE2) decoy that competes with endogenous ACE2 for binding of the SARS-CoV-2 spike receptor binding domain (S RBD) and inhibits infection may offer a therapeutic option with sustained efficacy against variants. Here, we used Molecular Dynamics (MD) simulation to predict ACE2 sequence substitutions that might increase its affinity for S RBD and screened candidate ACE2 decoys in vitro. The lead ACE2(T27Y/H34A)-IgG1FC fusion protein with enhanced S RBD affinity shows greater live SARS-CoV-2 virus neutralization capability than wild type ACE2. MD simulation was used to predict the effects of S RBD variant mutations on decoy affinity that was then confirmed by testing of an ACE2 Triple Decoy that included an additional enzyme activity-deactivating H374N substitution against mutated S RBD. The ACE2 Triple Decoy maintains high affinity for mutated S RBD, displays enhanced affinity for S RBD N501Y or L452R, and has the highest affinity for S RBD with both E484K and N501Y mutations, making it a viable therapeutic option for the prevention or treatment of SARS-CoV-2 infection with a high likelihood of efficacy against variants.

thermocellum has potential to be a CBP organism, issues such as low transformation efficiency (28).. ." should read "Although C. thermocellum has potential to be a CBP organism, issues such as low transformation efficiency, as pointed out by Tripathi et al. (26).. .." Page 2733: Reference 26 should read as follows: 26. Tripathi SA, et al. 2010. Development of pyrF-based genetic system for targeted gene deletion in Clostridium thermocellum and creation of a pta mutant. Appl. Environ. Microbiol. 76:6591-6599.