Parallel evolution of alternate morphotypes of Chryseobacterium gleum during experimental evolution with Caenorhabditis elegans Open Access
Duckett, Marissa (Summer 2023)
Published
Abstract
Microbial communities shape every organism and environment, and shifts in these communities can cause systemic change within a host that can ultimately affect host health. Understanding how multiple species evolve under the influence of each other in contrast to independently is important for acquiring insight into evolution of community composition, and vice versa. Evolution of community composition is not well understood, but previous research has revealed that community composition converges over evolutionary time. In this investigation, twelve slightly variable communities were created and followed over ten passages in Caenorhabditis elegans hosts. Upon the sixth passage, variable morphotypes were observed and maintained as the experiment progressed. We aim to understand what selective pressures could have contributed to this differentiation and maintenance of variable morphotypes. Chryseobacterium gleum had the greatest relative abundance in these host associated communities and developed alternate morphologies in two of the twelve communities. Common phenotypes, growth rate, carrying capacity, and motility were measured in hopes of revealing causes for this morphotype differentiation. Growth rate and carrying capacity suggest adaptation to the environment rather than evolution to the inside of the host. Motility was a more useful gauge for variability in these morphotypes, revealing consistently less spread in alternate morphs than original morphs. Gliding motility was confirmed through genomics, but no variability was observed in genetic elements responsible for gliding motility, the Gld proteins and T9SS genes, between alternate, original, and ancestral isolates. Previous research observed an increase in motility as nutrient concentration decreased. Our results did not show this trend, indicating that there are differences in how motility is regulated in Chryseobacterium. Although community composition converges over time, microbial lineages evolve differently, likely due to adaptation to environment and regulatory differences in response to unknown selective pressures.
Table of Contents
INTRODUCTION 1
RESULTS 3
C. gleum is a worm pathogen 9
There is variability within community and passage and between isolates 10
Growth rate is lower and carrying capacity is greater in alternate morphs than ancestor 11
Pairwise competition in vitro 14
Alternate morphs are less motile than original morphs 18
There is no observable trend in motility of original morphotypes during adaptation 20
Genomic analysis reveals no variability in gliding genes 22
Regulation of motility by nutrient concentration 26
DISCUSSION 35
METHODS 40
Strains and culture conditions 40
Community-based experimental evolution 41
Pairwise bacterial interactions in vitro 43
Chryseobacterium gleum Mortality Assays 44
Surface motility 45
Data availability 47
TABLE OF FIGURES 47
REFERENCES 66
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Parallel evolution of alternate morphotypes of Chryseobacterium gleum during experimental evolution with Caenorhabditis elegans () | 2023-07-15 21:42:55 -0400 |
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