Zinc’ing it out: zinc homeostasis mechanisms and their impact on the pathogenesis of human pathogen group A streptococcus

Makthal, Nishanth; Kumaraswami, Muthiah

doi:10.1039/c7mt00240h

Cited by 20 publications

(39 citation statements)

References 80 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…4). S. uberis contains the ATP-binding cassette (ABC) permease AdcABC, a conserved zinc acquisition system among streptococci (37). We observed that the zinc-specific solute binding protein (SBP), adcA (CGZ53_03345), was downregulated 4.5 log 2 -fold in response to PBT2zinc ( Fig.…”

Section: Resultsmentioning

confidence: 89%

Multiple Bactericidal Mechanisms of the Zinc Ionophore PBT2

Harbison-Price

Ferguson

Heikal

et al. 2020

mSphere

View full text Add to dashboard Cite

Globally, more antimicrobials are used in food-producing animals than in humans, and the extensive use of medically important human antimicrobials poses a significant public health threat in the face of rising antimicrobial resistance (AMR). The development of novel ionophores, a class of antimicrobials used exclusively in animals, holds promise as a strategy to replace or reduce essential human antimicrobials in veterinary practice. PBT2 is a zinc ionophore with recently demonstrated antibacterial activity against several Gram-positive pathogens, although the underlying mechanism of action is unknown. Here, we investigated the bactericidal mechanism of PBT2 in the bovine mastitis-causing pathogen, Streptococcus uberis. In this work, we show that PBT2 functions as a Zn2+/H+ ionophore, exchanging extracellular zinc for intracellular protons in an electroneutral process that leads to cellular zinc accumulation. Zinc accumulation occurs concomitantly with manganese depletion and the production of reactive oxygen species (ROS). PBT2 inhibits the activity of the manganese-dependent superoxide dismutase, SodA, thereby impairing oxidative stress protection. We propose that PBT2-mediated intracellular zinc toxicity in S. uberis leads to lethality through multiple bactericidal mechanisms: the production of toxic ROS and the impairment of manganese-dependent antioxidant functions. Collectively, these data show that PBT2 represents a new class of antibacterial ionophores capable of targeting bacterial metal ion homeostasis and cellular redox balance. We propose that this novel and multitarget mechanism of PBT2 makes the development of cross-resistance to medically important antimicrobials unlikely. IMPORTANCE More antimicrobials are used in food-producing animals than in humans, and the extensive use of medically important human antimicrobials poses a significant public health threat in the face of rising antimicrobial resistance. Therefore, the elimination of antimicrobial crossover between human and veterinary medicine is of great interest. Unfortunately, the development of new antimicrobials is an expensive high-risk process fraught with difficulties. The repurposing of chemical agents provides a solution to this problem, and while many have not been originally developed as antimicrobials, they have been proven safe in clinical trials. PBT2, a zinc ionophore, is an experimental therapeutic that met safety criteria but failed efficacy checkpoints against both Alzheimer’s and Huntington’s diseases. It was recently found that PBT2 possessed potent antimicrobial activity, although the mechanism of bacterial cell death is unresolved. In this body of work, we show that PBT2 has multiple mechanisms of antimicrobial action, making the development of PBT2 resistance unlikely.

show abstract

Section: Resultsmentioning

confidence: 89%

Multiple Bactericidal Mechanisms of the Zinc Ionophore PBT2

Harbison-Price

Ferguson

Heikal

et al. 2020

mSphere

View full text Add to dashboard Cite

show abstract

“…Zinc is an essential micronutrient for all organisms, serves as a structural or catalytic cofactor in 5 to 6% of proteins in the bacterial proteome (22)(23)(24), and can play an important role in the expression of key virulence factors (25)(26)(27)(28)(29)(30)(31)(32). However, high concentrations of zinc are toxic, possibly due to competition with other relevant metal ions (24,33), inhibition of key enzymes and essential metabolic reactions in the cell (32,34,35), and/or induction of membrane stress (36).…”

mentioning

confidence: 99%

Availability of Zinc Impacts Interactions between Streptococcus sanguinis and Pseudomonas aeruginosa in Coculture

Gifford

Hampton

et al. 2020

J Bacteriol

View full text Add to dashboard Cite

Airway infections associated with cystic fibrosis (CF) are polymicrobial. We reported previously that clinical isolates of Pseudomonas aeruginosa promote the growth of a variety of streptococcal species. To explore the mechanistic basis of this interaction, we performed a genetic screen to identify mutants of Streptococcus sanginuis SK36 whose growth was no longer enhanced by P. aeruginosa PAO1. Mutations in the zinc uptake systems of S. sanguinis SK36 reduced growth of these strains by 1 to 3 logs compared to that of wild-type S. sanguinis SK36 when grown in coculture with P. aeruginosa PAO1, and exogenous zinc (0.1 to 10 μM) rescued the coculture defect of zinc uptake mutants of S. sanguinis SK36. Zinc uptake mutants of S. sanguinis SK36 had no obvious growth defect in monoculture. Consistent with competition for zinc driving coculture dynamics, S. sanguinis SK36 grown in coculture with P. aeruginosa showed increased expression of zinc uptake genes compared to that of S. sanguinis grown alone. Strains of P. aeruginosa PAO1 defective in zinc transport also supported ∼2-fold more growth by S. sanguinis compared to that in coculture with wild-type P. aeruginosa PAO1. An analysis of 118 CF sputum samples revealed that total zinc levels varied from ∼5 to 145 μM. At relatively low zinc levels, Pseudomonas and Streptococcus spp. were found in approximately equal abundance; at higher zinc levels, we observed a decline in relative abundance of Streptococcus spp., perhaps as a result of increasing zinc toxicity. Together, our data indicate that the relative abundances of these microbes in the CF airway may be impacted by zinc levels. IMPORTANCE Polymicrobial infections in CF cases likely impact patient health, but the mechanism(s) underlying such interactions is poorly understood. Here, we show using an in vitro model system that interactions between Pseudomonas and Streptococcus are modulated by zinc availability, and clinical data are consistent with this model. Together with previous studies, our work supports a role for metal homeostasis as a key factor driving microbial interactions.

show abstract

“…2B,C), which are involved in many crucial biological processes and are essential for bacterial survival in the environment or in the infected host (28). In particular, zinc has recently been shown to be essential for pathogenic streptococci in their growth, morphology and virulence during infection (42, 43).…”

Section: Resultsmentioning

confidence: 99%

“…Similarly, several zinc transporters have been identified to contribute to zinc homeostasis and virulence in pathogenic streptococci (42, 43). In most streptococci, zinc acquisition involves a high-affinity zinc-ABC transporter, which is comprised of an integral membrane component (AdcB), an ATPase (AdcC) and one or several zinc-binding proteins (AdcA, AdcAII, Lbp, or Lmb) (42, 44–46).…”

Section: Introductionmentioning

confidence: 99%

“…Recent studies have suggested that total zinc levels are much higher in sputum from CF patients compared with healthy controls (48), but zinc availability is limited in the lung mucosa, leading to zinc starvation for P. aeruginosa during CF lung infection (49). Moreover, the host also employs zinc starvation or intoxication to retard streptococcal growth during colonization and infection (42, 43, 50). Nevertheless, the potential significance of zinc in the interplay between P. aeruginosa and Streptococcus , especially in the context of a polymicrobial infection in the CF airway, remains to be explored.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Availability of Zinc Impacts Interactions BetweenStreptococcus sanguinisandPseudomonas aeruginosain Co-culture

Gifford

Hampton

et al. 2019

Preprint

View full text Add to dashboard Cite

23Airway infections associated with cystic fibrosis (CF) are polymicrobial. We reported 24 previously that clinical isolates of P. aeruginosa promote the growth of a variety of 25 streptococcal species. To explore the mechanistic basis of this interaction, we performed a 26 genetic screen to identify mutants of Streptococcus sanginuis SK36 whose growth was no 27 longer enhanced by P. aeruginosa PAO1. Mutations in zinc uptake systems of S. sanginuis 28 SK36 reduced growth of these strains by 1-3 log compared to wild-type S. sanginuis SK36 29 when grown in coculture with P. aeruginosa PA01, while exogenous zinc (0.1-10 μm) rescued 30 the coculture defect of zinc uptake mutants of S. sanginuis SK36. Zinc uptake mutants of S. 31 sanginuis SK36 had no obvious growth defect in monoculture. Consistent with a competition 32 for zinc driving coculture dynamics, S. sanginuis SK36 grown in coculture with P. aeruginosa 33 showed increased expression of zinc uptake genes compared to S. sanginuis grown alone. 34 Strains of P. aeruginosa PAO1 defective in zinc transport also supported more robust growth 35 by S. sanginuis compared to coculture with wild-type P. aeruginosa PAO1. An analysis of 118 36 CF sputum samples revealed that total zinc levels varied from ~5-145 μM. At relatively low 37 zinc levels, Pseudomonas and Streptococcus were found in approximately equal abundance; 38 at higher zinc levels, we observed an increasing relative abundance of Pseudomonas and 39 decline of Streptococcus, perhaps as a result of increasing zinc toxicity. Together, our data 40 indicate that the relative abundance of these microbes in the CF airway may be impacted by 41 zinc levels. 42 IMPORTANCE. Polymicrobial infections in CF likely impact patient health, but the 43 mechanism(s) underlying such interactions are poorly understood. Here we show that 44 interactions between Pseudomonas and Streptococcus are modulated by zinc availability 45 using an in vitro model system, and clinical data are consistent with this model. Together with 46 previous studies, our work supports a role for metal homeostasis as a key factor driving 47 49Cystic fibrosis (CF) is a monogenic autosomal recessive disorder caused by mutations in the 50 cystic fibrosis transmembrane conductance regulator (CFTR) gene (1). It is estimated that 51 ~70,000 individuals in the world are affected by CF and the most common mutation, caused 52 by a deletion of phenylalanine at the 508th amino acid within the CFTR protein (ΔF508), is 53 found in approximately 70% of this population (2, 3). CFTR dysfunction affects several body 54 systems, and progressive lung disease due to chronic and recurrent microbial infections is 55 the leading cause of morbidity and mortality in individuals with CF (4, 5). It has been shown 56 that CF airway infections are polymicrobial (6, 7), and the composition and interspecies 57 interactions within the polymicrobial communities can have profound and diverse 58 consequences, including on bacterial growth (8-10), as well as disease progression and 59 thera...

show abstract

Zinc’ing it out: zinc homeostasis mechanisms and their impact on the pathogenesis of human pathogen group A streptococcus

Cited by 20 publications

References 80 publications

Multiple Bactericidal Mechanisms of the Zinc Ionophore PBT2

Multiple Bactericidal Mechanisms of the Zinc Ionophore PBT2

Availability of Zinc Impacts Interactions between Streptococcus sanguinis and Pseudomonas aeruginosa in Coculture

Availability of Zinc Impacts Interactions BetweenStreptococcus sanguinisandPseudomonas aeruginosain Co-culture

Contact Info

Product

Resources

About