Increased Zinc Availability Enhances Initial Aggregation and Biofilm Formation of Streptococcus pneumoniae

Abstract

Bacteria growing within biofilms are protected from antibiotics and the immune system. Within these structures, horizontal transfer of genes encoding virulence factors, and promoting antibiotic resistance occurs, making biofilms an extremely important aspect of pneumococcal colonization and persistence. Identifying environmental cues that contribute to the formation of biofilms is critical to understanding pneumococcal colonization and infection. Iron has been shown to be essential for the formation of pneumococcal biofilms; however, the role of other physiologically important metals such as copper, zinc, and manganese has been largely neglected. In this study, we investigated the effect of metals on pneumococcal aggregation and early biofilm formation. Our results show that biofilms increase as zinc concentrations increase. The effect was found to be zinc-specific, as altering copper and manganese concentrations did not affect biofilm formation. Scanning electron microscopy analysis revealed structural differences between biofilms grown in varying concentrations of zinc. Analysis of biofilm formation in a mutant strain lacking the peroxide-generating enzyme pyruvate oxidase, SpxB, revealed that zinc does not protect against pneumococcal H2O2. Further, analysis of a mutant strain lacking the major autolysin, LytA, indicated the role of zinc as a negative regulator of LytA-dependent autolysis, which could affect biofilm formation. Additionally, analysis of cell-cell aggregation via plating and microscopy revealed that high concentrations of zinc contribute to intercellular interaction of pneumococci. The findings from this study demonstrate that metal availability contributes to the ability of pneumococci to form aggregates and subsequently, biofilms.

Electrophoretic Determination of Lactococcus lactis Modified by Zinc Ions

“…Those results were confirmed by data collected from the AFM study which pointed out that addition of Zn 2+ greatly changed the adhesive properties of microbial surface and caused formation of bacterial agglomerates. Brown et al [35] also investigated the influence of the zinc on the biofilms formation and their results shown that with the Zn 2+ concentrations increase, the aggregation of bacteria rise too. The described effect was found to be zinc-specific, because another types of ions (copper and manganese) did not affect biofilm formation.…”

Asian Sand Dust Particles Increased Pneumococcal Biofilm Formation in vitro and Colonization in Human Middle Ear Epithelial Cells and Rat Middle Ear Mucosa

“…The pneumococcal growth was detected by measuring optical density at 600 nm (OD 600 ) at different time points. S. pneumoniae planktonic growth was also evaluated by detecting metabolically active bacteria by resazurin staining after 48 h. Bacteria were grown in metal ion-free BHI medium based on a previous report (BHI medium treated with chelex-100) (Brown et al, 2017). In vitro biofilm formation ability of the bacteria, in the presence of ASD, was evaluated using a static microtiter plate assay (Christensen et al, 1982;Yadav et al, 2018).…”

Opening the OPK Assay Gatekeeper: Harnessing Multi-Modal Protection by Pneumococcal Vaccines

“…A more complex approach is needed to ascertain effective blockade of the biofilm formation known to participate in nasopharyngeal colonization and otitis media. Many of the steps in biofilm formation cross over into bacterial aggregation (discussed above) [31,32]. It is clear that the physiology of biofilms and virulence extends to changes in bacterial behavior such as competence and fratricide [33][34][35][36].…”