Clinical microbiology

Cellular arrangement impacts metabolic activity and antibiotic tolerance in Pseudomonas aeruginosa biofilms

Cells must access resources to survive, and the anatomy of multicellular structures influences this access. In diverse multicellular eukaryotes, resources are provided by internal conduits that allow substances to travel more readily through tissue than they would via diffusion. Microbes growing in multicellular structures, called biofilms, are also affected by differential access to resources and we hypothesized that this is influenced by the physical arrangement of the cells. In this study, we examined the microanatomy of biofilms formed by the pathogenic bacterium Pseudomonas aeruginosa and discovered that clonal cells form striations that are packed lengthwise across most of a mature biofilm's depth. We identified mutants, including those defective in pilus function and in O-antigen attachment, that show alterations to this lengthwise packing phenotype. Consistent with the notion that cellular arrangement affects access to resources within the biofilm, we found that while the wild type shows even distribution of tested substrates across depth, the mutants show accumulation of substrates at the biofilm boundaries. Furthermore, we found that altered cellular arrangement within biofilms affects the localization of metabolic activity, the survival of resident cells, and the susceptibility of subpopulations to antibiotic treatment. Our observations provide insight into cellular features that determine biofilm microanatomy, with consequences for physiological differentiation and drug sensitivity.

Cell arrangement impacts metabolic activity and antibiotic tolerance in Pseudomonas aeruginosa biofilms

Cells must access resources to survive, and the anatomy of multicellular structures influences this access. In diverse multicellular eukaryotes, resources are provided by internal conduits that allow substances to travel more readily through tissue than they would via diffusion. Microbes growing in multicellular structures, called biofilms, are also affected by differential access to resources and we hypothesized that this is influenced by the physical arrangement of the cells. In this study, we examined the microanatomy of biofilms formed by the pathogenic bacterium Pseudomonas aeruginosa and discovered that clonal cells form striations that are packed lengthwise across most of a mature biofilm's depth. We identified mutants, including those defective in pilus function and in O-antigen attachment, that show alterations to this lengthwise packing phenotype. Consistent with the notion that cellular arrangement affects access to resources within the biofilm, we found that while the wild type shows even distribution of tested substrates across depth, the mutants show accumulation of substrates at the biofilm boundaries. Furthermore, we found that altered cellular arrangement within biofilms affects the localization of metabolic activity, the survival of resident cells, and the susceptibility of subpopulations to antibiotic treatment. Our observations provide insight into cellular features that determine biofilm microanatomy, with consequences for physiological differentiation and drug sensitivity.

Spatial and Temporal Persistence of Fluorescent Lactiplantibacillus plantarum RS-09 in Intestinal Tract

The beneficial effects of the probiotic strain Lactiplantibacillus plantarum (formerly Lactobacillus plantarum) are based on its adherence and colonization ability in the gut. However, little is known about the migration and long-term gut colonization of the strain. This study evaluated the gut colonization modes of Lactiplantibacillus plantarum RS-09 to identify the strain with long-term gut colonization potential. We established CFDA/SE-labeled RS-09 to study the temporal and spatial distribution of RS-09 in the intestine as well as to analyze its persistence in different parts of the intestine by flow cytometry. This study has shown that the RS-09 strain maintains strong adhesion abilities under acid (pH 2.5) and base (pH 8.5) conditions. In addition, CFDA/SE can be used as an indicator for the labeling of L. plantarum RS-09 in the intestinal tract in vivo. We established a growth kinetics model of RS-09 to elucidate its persistence in the intestine. In vivo persistence experiments showed that the persistence rate of RS-09 was the highest in the cecum (69.5%) and the lowest in the duodenum (12.8%) at 96 h. After 20 days, RS-09 was predominantly localized in the cecum and colon steadily. These studies provide new insights into the long-term persistence of L. plantarum in the gastrointestinal tract. The CFDA/SE label system may be used to study the in vivo colonization dynamics of other probiotic strains.