Substrate-dependent cluster density dynamics of Corynebacterium glutamicum phosphotransferase system permeases

Enhanced L-ornithine production from glucose and sucrose via manipulation of the fructose metabolic pathway in Corynebacterium glutamicum

L-Ornithine, an important non-essential amino acid, has considerable medicinal value in the treatment of complex liver diseases. Microbial fermentation strategies using robust engineered strains have remarkable potential for producing L-ornithine. We showed that glucose and sucrose co-utilization accumulate more L-ornithine in Corynebacterium glutamicum than glucose alone. Further manipulating the expression of intracellular fructose-1-phosphate kinase through the deletion of pfkB1resulted in the engineered strain C. glutamicum SO30 that produced 47.6 g/L of L-ornithine, which represents a 32.8% increase than the original strain C. glutamicum SO26 using glucose as substrate (35.88 g/L). Moreover, fed-batch cultivation of C. glutamicum SO30 in 5-L fermenters produced 78.0 g/L of L-ornithine, which was a 78.9% increase in yield compared with that produced by C. glutamicum SO26. These results showed that manipulating the fructose metabolic pathway increases L-ornithine accumulation and provides a reference for developing C. glutamicum to produce valuable metabolites.

Subcellular Dynamics of a Conserved Bacterial Polar Scaffold Protein

In order to survive, bacterial cells rely on precise spatiotemporal organization and coordination of essential processes such as cell growth, chromosome segregation, and cell division. Given the general lack of organelles, most bacteria are forced to depend on alternative localization mechanisms, such as, for example, geometrical cues. DivIVA proteins are widely distributed in mainly Gram-positive bacteria and were shown to bind the membrane, typically in regions of strong negative curvature, such as the cell poles and division septa. Here, they have been shown to be involved in a multitude of processes: from apical cell growth and chromosome segregation in actinobacteria to sporulation and inhibition of division re-initiation in firmicutes. Structural analyses revealed that DivIVA proteins can form oligomeric assemblies that constitute a scaffold for recruitment of other proteins. However, it remained unclear whether interaction with partner proteins influences DivIVA dynamics. Using structured illumination microscopy (SIM), single-particle tracking (SPT) microscopy, and fluorescent recovery after photobleaching (FRAP) experiments, we show that DivIVA from Corynebacterium glutamicum is mobilized by its binding partner ParB. In contrast, we show that the interaction between Bacillus subtilis DivIVA and its partner protein MinJ reduces DivIVA mobility. Furthermore, we show that the loss of the rod-shape leads to an increase in DivIVA dynamics in both organisms. Taken together, our study reveals the modulation of the polar scaffold protein by protein interactors and cell morphology. We reason that this leads to a very simple, yet robust way for actinobacteria to maintain polar growth and their rod-shape. In B. subtilis, however, the DivIVA protein is tailored towards a more dynamic function that allows quick relocalization from poles to septa upon division.

Application of Corynebacterium glutamicum engineering display system in three generations of biorefinery

The fermentation production of platform chemicals in biorefineries is a sustainable alternative to the current petroleum refining process. The natural advantages of Corynebacterium glutamicum in carbon metabolism have led to C. glutamicum being used as a microbial cell factory that can use various biomass to produce value-added platform chemicals and polymers. In this review, we discussed the use of C. glutamicum surface display engineering bacteria in the three generations of biorefinery resources, and analyzed the C. glutamicum engineering display system in degradation, transport, and metabolic network reconstruction models. These engineering modifications show that the C. glutamicum engineering display system has great potential to become a cell refining factory based on sustainable biomass, and further optimizes the inherent properties of C. glutamicum as a whole-cell biocatalyst. This review will also provide a reference for the direction of future engineering transformation.

Elongation factor P is required for EIIGlc translation in Corynebacterium glutamicum due to an essential polyproline motif

Translating ribosomes require elongation factor P (EF-P) to incorporate consecutive prolines (XPPX) into nascent peptide chains. The proteome of Corynebacterium glutamicum ATCC 13032 contains a total of 1,468 XPPX motifs, many of which are found in proteins involved in primary and secondary metabolism. We show here that synthesis of EII^Glc , the glucose-specific permease of the phosphoenolpyruvate (PEP): sugar phosphotransferase system (PTS) encoded by ptsG, is strongly dependent on EF-P, as an efp deletion mutant grows poorly on glucose as sole carbon source. The amount of EII^Glc is strongly reduced in this mutant, which consequently results in a lower rate of glucose uptake. Strikingly, the XPPX motif is essential for the activity of EII^Glc , and substitution of the prolines leads to inactivation of the protein. Finally, translation of GntR2, a transcriptional activator of ptsG, is also dependent on EF-P. However, its reduced amount in the efp mutant can be compensated for by other regulators. These results reveal for the first time a translational bottleneck involving production of the major glucose transporter EII^Glc , which has implications for future strain engineering strategies.

Cryptic-Prophage-Encoded Small Protein DicB Protects Escherichia coli from Phage Infection by Inhibiting Inner Membrane Receptor Proteins

Temperate bacteriophages can integrate their genomes into the bacterial host chromosome and exist as prophages whose gene products play key roles in bacterial fitness and interactions with eukaryotic host organisms. Most bacterial chromosomes contain “cryptic” prophages that have lost genes required for production of phage progeny but retain genes of unknown function that may be important for regulating bacterial host physiology. This study provides such an example, where a cryptic-prophage-encoded product can perform multiple roles in the bacterial host and influence processes, including metabolism, cell division, and susceptibility to phage infection. Further functional characterization of cryptic-prophage-encoded functions will shed new light on host-phage interactions and their cellular physiological implications.

Bacterial genomes harbor cryptic prophages that have lost genes required for induction, excision from host chromosomes, or production of phage progeny. Escherichia coli K-12 strains contain a cryptic prophage, Qin, that encodes a small RNA, DicF, and a small protein, DicB, that have been implicated in control of bacterial metabolism and cell division. Since DicB and DicF are encoded in the Qin immunity region, we tested whether these gene products could protect the E. coli host from bacteriophage infection. Transient expression of the dicBF operon yielded cells that were ∼100-fold more resistant to infection by λ phage than control cells, and the phenotype was DicB dependent. DicB specifically inhibited infection by λ and other phages that use ManYZ membrane proteins for cytoplasmic entry of phage DNA. In addition to blocking ManYZ-dependent phage infection, DicB also inhibited the canonical sugar transport activity of ManYZ. Previous studies demonstrated that DicB interacts with MinC, an FtsZ polymerization inhibitor, causing MinC localization to midcell and preventing Z ring formation and cell division. In strains producing mutant MinC proteins that do not interact with DicB, both DicB-dependent phenotypes involving ManYZ were lost. These results suggest that DicB is a pleiotropic regulator of bacterial physiology and cell division and that these effects are mediated by a key molecular interaction with the cell division protein MinC.

IMPORTANCE Temperate bacteriophages can integrate their genomes into the bacterial host chromosome and exist as prophages whose gene products play key roles in bacterial fitness and interactions with eukaryotic host organisms. Most bacterial chromosomes contain “cryptic” prophages that have lost genes required for production of phage progeny but retain genes of unknown function that may be important for regulating bacterial host physiology. This study provides such an example, where a cryptic-prophage-encoded product can perform multiple roles in the bacterial host and influence processes, including metabolism, cell division, and susceptibility to phage infection. Further functional characterization of cryptic-prophage-encoded functions will shed new light on host-phage interactions and their cellular physiological implications.

Phase separation and clustering of an ABC transporter in Mycobacterium tuberculosis

Phase separation drives numerous cellular processes, ranging from the formation of membrane-less organelles to the cooperative assembly of signaling proteins. Features such as multivalency and intrinsic disorder that enable condensate formation are found not only in cytosolic and nuclear proteins, but also in membrane-associated proteins. The ABC transporter Rv1747, which is important for Mycobacterium tuberculosis (Mtb) growth in infected hosts, has a cytoplasmic regulatory module consisting of 2 phosphothreonine-binding Forkhead-associated domains joined by an intrinsically disordered linker with multiple phospho-acceptor threonines. Here we demonstrate that the regulatory modules of Rv1747 and its homolog in Mycobacterium smegmatis form liquid-like condensates as a function of concentration and phosphorylation. The serine/threonine kinases and sole phosphatase of Mtb tune phosphorylation-enhanced phase separation and differentially colocalize with the resulting condensates. The Rv1747 regulatory module also phase-separates on supported lipid bilayers and forms dynamic foci when expressed heterologously in live yeast and M. smegmatis cells. Consistent with these observations, single-molecule localization microscopy reveals that the endogenous Mtb transporter forms higher-order clusters within the Mycobacterium membrane. Collectively, these data suggest a key role for phase separation in the function of these mycobacterial ABC transporters and their regulation via intracellular signaling.