Inoculum Concentration Influences Pseudomonas aeruginosa Phenotype and Biofilm Architecture
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Inoculum Concentration Influences Pseudomonas aeruginosa Phenotype and Biofilm Architecture. / Lichtenberg, Mads; Kvich, Lasse; Larsen, Sara Louise Borregaard; Jakobsen, Tim Holm; Bjarnsholt, Thomas.
In: Microbiology Spectrum, Vol. 10, No. 6, 2022.Research output: Contribution to journal › Journal article › peer-review
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TY - JOUR
T1 - Inoculum Concentration Influences Pseudomonas aeruginosa Phenotype and Biofilm Architecture
AU - Lichtenberg, Mads
AU - Kvich, Lasse
AU - Larsen, Sara Louise Borregaard
AU - Jakobsen, Tim Holm
AU - Bjarnsholt, Thomas
N1 - Publisher Copyright: Copyright © 2022 Lichtenberg et al.
PY - 2022
Y1 - 2022
N2 - In infections, bacterial cells are often found as relatively small multicellular aggregates characterized by a heterogeneous distribution of phenotype, genotype, and growth rates depending on their surrounding microenvironment. Many laboratory models fail to mimic these characteristics, and experiments are often initiated from planktonic bacteria given optimal conditions for rapid growth without concerns about the microenvironmental characteristics during biofilm maturation. Therefore, we investigated how the initial bacterial concentration (henceforth termed the inoculum) influences the microenvironment during initial growth and how this affects the sizes and distribution of developed aggregates in an embedded biofilm model—the alginate bead biofilm model. Following 24 h of incubation, the viable biomass was independent of starting inoculum but with a radically different microenvironment which led to differences in metabolic activity depending on the inoculum. The inoculum also affected the number of cells surviving treatment with the antibiotic tobramycin, where the highest inoculum showed higher survival rates than the lowest inoculum. The change in antibiotic tolerance was correlated with cell-specific RNA content and O2 consumption rates, suggesting a direct role of metabolic activity. Thus, the starting number of bacteria results in different phenotypic trajectories governed by different microenvironmental characteristics, and we demonstrate some of the possible implications of such physiological gradients on the outcome of in vitro experiments.
AB - In infections, bacterial cells are often found as relatively small multicellular aggregates characterized by a heterogeneous distribution of phenotype, genotype, and growth rates depending on their surrounding microenvironment. Many laboratory models fail to mimic these characteristics, and experiments are often initiated from planktonic bacteria given optimal conditions for rapid growth without concerns about the microenvironmental characteristics during biofilm maturation. Therefore, we investigated how the initial bacterial concentration (henceforth termed the inoculum) influences the microenvironment during initial growth and how this affects the sizes and distribution of developed aggregates in an embedded biofilm model—the alginate bead biofilm model. Following 24 h of incubation, the viable biomass was independent of starting inoculum but with a radically different microenvironment which led to differences in metabolic activity depending on the inoculum. The inoculum also affected the number of cells surviving treatment with the antibiotic tobramycin, where the highest inoculum showed higher survival rates than the lowest inoculum. The change in antibiotic tolerance was correlated with cell-specific RNA content and O2 consumption rates, suggesting a direct role of metabolic activity. Thus, the starting number of bacteria results in different phenotypic trajectories governed by different microenvironmental characteristics, and we demonstrate some of the possible implications of such physiological gradients on the outcome of in vitro experiments.
KW - alginate bead
KW - biofilm
KW - microenvironment
KW - model system
KW - oxygen
KW - Pseudomonas aeruginosa
KW - spatial structure
U2 - 10.1128/spectrum.03131-22
DO - 10.1128/spectrum.03131-22
M3 - Journal article
C2 - 36354337
AN - SCOPUS:85144635991
VL - 10
JO - Microbiology spectrum
JF - Microbiology spectrum
SN - 2165-0497
IS - 6
ER -
ID: 333619337