Maple compounds prevent biofilm formation in via sortase inhibition.

The Pss exopolysaccharide (EPS) enhances the ability of the foodborne pathogen to colonize and persist on surfaces of fresh fruits and vegetables. Eradicating listeria within EPS-rich biofilms is challenging due to their increased tolerance to disinfectants, desiccation, and other stressors. Recently, we discovered that extracts of maple wood, including maple sap, are a potent source of antibiofilm agents.

Robust inducible gene expression in intracellular .

Attenuated strains of the intracellular pathogen can deliver genetically encoded payloads inside tumor cells. preferentially accumulates and propagates inside immune-suppressed tumor microenvironments. To maximize the payload impact in tumors and minimize damage to healthy tissues, it is desirable to induce payload synthesis when bacteria are eliminated from the healthy tissues but are grown to high numbers intratumorally.

Lignan-containing maple products inhibit biofilms on fresh produce.

Major listeriosis outbreaks have been associated with fresh produce contaminated with . Strains that synthesize the Pss exopolysaccharide (EPS) have an estimated 10 to 10-fold advantage over nonsynthesizing strains in causing listeriosis. They more readily attach to the surfaces of fruit and vegetables forming EPS-biofilms that better withstand stresses associated with produce storage and consumption.

The exopolysaccharide significantly enhances colonization and survival on fresh produce.

Fresh produce contaminated with has caused major listeriosis outbreaks in the last decades. Our knowledge about components of the listerial biofilms formed on fresh produce and their roles in causing foodborne illness remains incomplete. Here, we investigated, for the first time, the role of the listerial Pss exopolysaccharide (EPS) in plant surface colonization and stress tolerance.

Antifungal weapons of Lysobacter, a mighty biocontrol agent.

Bacteria interact with fungi in a variety of ways to inhibit fungal growth, while the underlying mechanisms remain only partially characterized. The plant-beneficial Bacillus and Pseudomonas species are well-known antifungal biocontrol agents, whereas Lysobacter are far less studied. Members of Lysobacter are easy to grow in fermenters and are safe to humans, animals and plants.

Coordinated control of the type IV pili and c-di-GMP-dependent antifungal antibiotic production in Lysobacter by the response regulator PilR.

In the soil gammaproteobacterium Lysobacter enzymogenes, a natural fungal predator, the response regulator PilR controls type IV pili (T4P)-mediated twitching motility as well as synthesis of the heat-stable antifungal factor (HSAF). Earlier we showed that PilR acts via the second messenger, c-di-GMP; however, the mechanism remained unknown. Here, we describe how PilR, c-di-GMP signalling, and HSAF synthesis are connected.

A YajQ-LysR-like, cyclic di-GMP-dependent system regulating biosynthesis of an antifungal antibiotic in a crop-protecting bacterium, Lysobacter enzymogenes.

YajQ, a binding protein of the universal bacterial second messenger cyclic di-GMP (c-di-GMP), affects virulence in several bacterial pathogens, including Xanthomonas campestris. In this bacterium, YajQ interacts with the transcription factor LysR. Upon c-di-GMP binding, the whole c-di-GMP-YajQ-LysR complex is found to dissociate from DNA, resulting in virulence gene regulation.

Cyclic di-GMP-Mediated Regulation of Gene Transfer and Motility in Rhodobacter capsulatus.

Gene transfer agents (GTAs) are bacteriophage-like particles produced by several bacterial and archaeal lineages that contain small pieces of the producing cells' genomes that can be transferred to other cells in a process similar to transduction. One well-studied GTA is RcGTA, produced by the alphaproteobacterium RcGTA gene expression is regulated by several cellular regulatory systems, including the CckA-ChpT-CtrA phosphorelay. The transcription of multiple other regulator-encoding genes is affected by the response regulator CtrA, including genes encoding putative enzymes involved in the synthesis and hydrolysis of the second messenger bis-(3'-5')-cyclic dimeric GMP (c-di-GMP).

Inducible asymmetric cell division and cell differentiation in a bacterium.

Multicellular organisms achieve greater complexity through cell divisions that generate different cell types. We engineered a simple genetic circuit that induces asymmetric cell division and subsequent cell differentiation in Escherichia coli. The circuit involves a scaffolding protein, PopZ, that is stably maintained at a single cell pole over multiple asymmetric cell divisions.

Engineering Adenylate Cyclase Activated by Near-Infrared Window Light for Mammalian Optogenetic Applications.

Light in the near-infrared optical window (NIRW) penetrates deep through mammalian tissues, including the skull and brain tissue. Here we engineered an adenylate cyclase (AC) activated by NIRW light (NIRW-AC) and suitable for mammalian applications. To accomplish this goal, we constructed fusions of several bacteriophytochrome photosensory and bacterial AC modules using guidelines for designing chimeric homodimeric bacteriophytochromes.

Signaling specificity in the c-di-GMP-dependent network regulating antibiotic synthesis in Lysobacter.

Enzymes controlling intracellular second messengers in bacteria, such as c-di-GMP, often affect some but not other targets. How such specificity is achieved is understood only partially. Here, we present a novel mechanism that enables specific c-di-GMP-dependent inhibition of the antifungal antibiotic production.

Positive and Negative Regulation of Glycerol Utilization by the c-di-GMP Binding Protein PlzA in Borrelia burgdorferi.

, the causative agent of Lyme disease, encounters two disparate host environments during its enzootic life cycle, ticks and mammalian hosts. has a small genome that encodes a streamlined cyclic dimeric GMP (c-di-GMP) signaling system comprising a single diguanylate cyclase, Rrp1, and two phosphodiesterases. This system is essential for spirochete survival in ticks, in part because it controls the expression of the operon involved in glycerol utilization.

CodY-Mediated c-di-GMP-Dependent Inhibition of Mammalian Cell Invasion in Listeria monocytogenes.

Elevated levels of the second messenger c-di-GMP suppress virulence in diverse pathogenic bacteria, yet mechanisms are poorly characterized. In the foodborne pathogen , high c-di-GMP levels inhibit mammalian cell invasion. Here, we show that invasion is impaired because of the decreased expression levels of internalin genes whose products are involved in invasion.

Using Light-Activated Enzymes for Modulating Intracellular c-di-GMP Levels in Bacteria.

Signaling pathways involving second messenger c-di-GMP regulate various aspects of bacterial physiology and behavior. We describe the use of a red light-activated diguanylate cyclase (c-di-GMP synthase) and a blue light-activated c-di-GMP phosphodiesterase (hydrolase) for manipulating intracellular c-di-GMP levels in bacterial cells. We illustrate the application of these enzymes in regulating several c-di-GMP-dependent phenotypes, i.

Photoactivated cells link diagnosis and therapy.

A semiautonomous system enables implanted photoactivated cells to produce glucose-lowering hormones and maintain glucose homeostasis in diabetic mice (Shao , this issue).

Optogenetic Module for Dichromatic Control of c-di-GMP Signaling.

Many aspects of bacterial physiology and behavior, including motility, surface attachment, and the cell cycle, are controlled by cyclic di-GMP (c-di-GMP)-dependent signaling pathways on the scale of seconds to minutes. Interrogation of such processes in real time requires tools for introducing rapid and reversible changes in intracellular c-di-GMP levels. Inducing the expression of genes encoding c-di-GMP-synthetic (diguanylate cyclases) and -degrading (c-di-GMP phosphodiesterase) enzymes by chemicals may not provide adequate temporal control.

Optogenetic Manipulation of Cyclic Di-GMP (c-di-GMP) Levels Reveals the Role of c-di-GMP in Regulating Aerotaxis Receptor Activity in Azospirillum brasilense.

Bacterial chemotaxis receptors provide the sensory inputs that inform the direction of navigation in changing environments. Recently, we described the bacterial second messenger cyclic di-GMP (c-di-GMP) as a novel regulator of a subclass of chemotaxis receptors. In , c-di-GMP binds to a chemotaxis receptor, Tlp1, and modulates its signaling function during aerotaxis.

Lysobacter PilR, the Regulator of Type IV Pilus Synthesis, Controls Antifungal Antibiotic Production via a Cyclic di-GMP Pathway.

is a ubiquitous soil gammaproteobacterium that produces a broad-spectrum antifungal antibiotic, known as heat-stable antifungal factor (HSAF). To increase HSAF production for use against fungal crop diseases, it is important to understand how HSAF synthesis is regulated. To gain insights into transcriptional regulation of the HSAF synthesis gene cluster, we generated a library with deletion mutations in the genes predicted to encode response regulators of the two-component signaling systems in strain OH11.

Systematic Nomenclature for GGDEF and EAL Domain-Containing Cyclic Di-GMP Turnover Proteins of Escherichia coli.

In recent years, Escherichia coli has served as one of a few model bacterial species for studying cyclic di-GMP (c-di-GMP) signaling. The widely used E. coli K-12 laboratory strains possess 29 genes encoding proteins with GGDEF and/or EAL domains, which include 12 diguanylate cyclases (DGC), 13 c-di-GMP-specific phosphodiesterases (PDE), and 4 "degenerate" enzymatically inactive proteins.

Listeria monocytogenes exopolysaccharide: origin, structure, biosynthetic machinery and c-di-GMP-dependent regulation.

Elevated levels of the second messenger c-di-GMP activate biosynthesis of an unknown exopolysaccharide (EPS) in the food-borne pathogen Listeria monocytogenes. This EPS strongly protects cells against disinfectants and desiccation, indicating its potential significance for listerial persistence in the environment and for food safety. We analyzed the potential phylogenetic origin of this EPS, determined its complete structure, characterized genes involved in its biosynthesis and hydrolysis and identified diguanylate cyclases activating its synthesis.

Identification of bacterial guanylate cyclases.

The ability of bacteria to use cGMP as a second messenger has been controversial for decades. Recently, nucleotide cyclases from Rhodospirillum centenum, GcyA, and Xanthomonas campestris, GuaX, have been shown to possess guanylate cyclase activities. Enzymatic activities of these guanylate cyclases measured in vitro were low, which makes interpretation of the assays ambiguous.

Fifty ways to inhibit motility via cyclic di-GMP: the emerging Pseudomonas aeruginosa swarming story.

There are numerous ways by which cyclic dimeric GMP (c-di-GMP) inhibits motility. Kuchma et al. (S.