Many roads lead to Rome: Neutral phenotypes in microorganisms. Issue 8 (16th October 2019)

• Record Type: Journal Article
• Authors: Nanjundiah, Vidyanand
• Other Names: Brigandt Ingo guestEditor.
• Is Part Of: Journal of experimental zoology. Volume 332:Issue 8(2019)
• Page Start: 339
• Page End: 348
• Publication Date: 2019-10-16
• Subjects: adaptation -- cellular slime mould -- chimaera -- dictyostelium -- multicellularity -- neutral evolution; Developmental biology -- Periodicals; Evolution (Biology) -- Periodicals; Molecular evolution -- Periodicals; Zoology -- Periodicals; Evolution, Molecular -- Periodicals; Developmental Biology -- Periodicals; Zoology -- Periodicals; 591
• DOI: 10.1002/jez.b.22909
• Languages: English
• ISSNs: 1552-5007

Abstract

Abstract: John Bonner pointed out that microorganisms differ in several ways, some of which may reflect neutral phenotypic evolution. For making his case, Bonner referred to interspecies differences and morphological traits. Here we consider intraspecies differences and physiological traits. As a case‐study, we examine the production of an extracellular cyclic 3 ′, 5 ′ monophosphate phosphodiesterase in the cellular slime mold Dictyostelium discoideum . Temporal profiles of phosphodiesterase activity differ significantly between wild‐type strains. From that we argue that the inference drawn initially from studies on a single wild‐type, namely that the profile displayed by it pointed to an adaptive role, was mistaken. We generalize the conclusion to suggest that physiological differences exhibited by microorganisms of the same species may, but need not, reflect adaptations to different environments. Rather, the differences could be related to the fact that microorganisms live in groups whose composition can vary between homogeneous (clonal) and heterogeneous (polyclonal). More than one physiological profile is consistent with the normal development of the group in a given environment; the alternatives are neutral. When studying microbial physiology and behavior, it is expected that the observations are made on a clonal population; genetic (and so phenotypic) heterogeneity is carefully guarded against. As the example from D. discoideum shows, an unintended consequence of overlooking phenotypic heterogeneity is that one can fall into the trap of accepting a seemingly plausible, but possibly erroneous, adaptive explanation for a "normal" wild‐type phenotype. Abstract : Wild‐type strains of cellular slime moulds, with superficially indistinguishable life cycles, can manifest distinct physiological features. Also, they can participate in forming heterogeneous multicellular groups. Highlights: ● Microorganisms with asexual life cycles, such as the cellular slime molds (CSMs), can form equivalent clonal or polyclonal groups. ● In polyclonal groups, compatible individuals may differ in physiology. ● The differences appear to be selectively neutral at the group level.