Metabolic Allometric Scaling of Unicellular Organisms as a Product of Selection Guided by Optimization of Nutrients Distribution in Food Chains

📝 Abstract

One of the major characteristics of living organisms is metabolic rate, which is the amount of energy produced per unit of time. When the mass of organisms increases, the metabolic rate also increases (usually as a power function of mass), but usually slower than mass. This effect is called metabolic allometric scaling. Its causes are considered unknown. The effect has important implications for individual and population organismal development. It was shown in the first part of this study, presented in a separate paper, that in the case of multicellular organisms, this effect is a consequence of natural selection and optimization of nutrient distribution between the species of a food chain, sharing resources of a common habitat. Here, in the second part that studies unicellular organisms, we discover that the same principle of natural selection guided by optimization of nutrient distribution between the species of a food chain defines also metabolic allometric scaling of unicellular organisms. To find that, we consider the metabolic properties of Amoeba proteus, fission yeast Schizosaccharomyces pombe, Escherichia coli, Bacillus subtilis, Staphylococcus. The sharing of nutrients is optimized in such a way that bigger microorganisms have progressively bigger nutrient influx per unit of surface. This evolutionary arrangement secures the stability of a food chain by providing certain metabolic advantages for bigger organisms. Accounting for this regular increase of nutrient influx with mass increase, we obtained allometric exponents and their ranges close to experimental values, thus proving that metabolic allometric scaling of both multicellular and unicellular organisms is defined by the same fundamental evolutionary principle of optimized sharing of nutrients between the species of a food chain.

💡 Analysis

One of the major characteristics of living organisms is metabolic rate, which is the amount of energy produced per unit of time. When the mass of organisms increases, the metabolic rate also increases (usually as a power function of mass), but usually slower than mass. This effect is called metabolic allometric scaling. Its causes are considered unknown. The effect has important implications for individual and population organismal development. It was shown in the first part of this study, presented in a separate paper, that in the case of multicellular organisms, this effect is a consequence of natural selection and optimization of nutrient distribution between the species of a food chain, sharing resources of a common habitat. Here, in the second part that studies unicellular organisms, we discover that the same principle of natural selection guided by optimization of nutrient distribution between the species of a food chain defines also metabolic allometric scaling of unicellular organisms. To find that, we consider the metabolic properties of Amoeba proteus, fission yeast Schizosaccharomyces pombe, Escherichia coli, Bacillus subtilis, Staphylococcus. The sharing of nutrients is optimized in such a way that bigger microorganisms have progressively bigger nutrient influx per unit of surface. This evolutionary arrangement secures the stability of a food chain by providing certain metabolic advantages for bigger organisms. Accounting for this regular increase of nutrient influx with mass increase, we obtained allometric exponents and their ranges close to experimental values, thus proving that metabolic allometric scaling of both multicellular and unicellular organisms is defined by the same fundamental evolutionary principle of optimized sharing of nutrients between the species of a food chain.

📄 Content

Metabolic Allometric Scaling of Unicellular Organisms as a Product of Selection Guided by Optimization of Nutrients Distribution in Food Chains Yuri K. Shestopalo® Consultant, Prof. Dr. Sci. (Phys.) Toronto, Ontario, Canada shes169@yahoo.ca Received 13 June 2024 Revised 16 September 2024 Accepted 23 September 2024 Published 7 November 2024 One of the major characteristics of living organisms is metabolic rate  the amount of energy produced per unit of time. When the mass of organisms increases, the metabolic rate also increases (as a power function of mass), but usually slower than mass. This e®ect is called metabolic allometric scaling. Its causes are considered unknown. The e®ect has important implications for individual and population organismal development. It was shown in the ¯rst part of this study, presented in a separate paper, that in the case of multicellular organisms, this e®ect is a consequence of natural selection and optimization of nutrient distribution between the species of a food chain, sharing resources of a common habitat. Here, in the second part that studies unicellular organisms, we discover that the same principle of natural selection guided by optimization of nutrient distribution between the species of a food chain de¯nes also metabolic allometric scaling of unicellular organisms. To ¯nd that, we consider the metabolic properties of Amoeba proteus, ¯ssion yeast Schizosaccharomyces pombe, Escherichia coli, Bacillus subtilis, Staphylococcus. The sharing of nutrients is optimized in such a way that bigger microorganisms have progressively bigger nutrient in°ux per unit of surface. This evolutionary arrangement secures the stability of a food chain by providing certain metabolic advantages for bigger organisms. Accounting for this regular increase of nutrient in°ux with mass increase, we obtained allometric exponents and their ranges close to experimental values, thus proving that metabolic allometric scaling of both multicellular and unicellular organisms is de¯ned by the same fundamental evolutionary principle of optimized sharing of nutrients between the species of a food chain. Keywords: Cells; food chain; common habitat; nutrients; metabolism; metabolic rate; balanced sharing of resources. This is an Open Access article published by World Scienti¯c Publishing Company. It is distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 (CC BY-NC) License, which permits use, distribution and reproduction in any medium, provided that the original work is properly cited and is used for non-commercial purposes. OPEN ACCESS Biophysical Reviews and Letters #.c The Author(s) DOI: 10.1142/S1793048024500097 1 Biophys. Rev. Lett. Downloaded from www.worldscientific.com by 176.100.43.138 on 11/11/24. Re-use and distribution is strictly not permitted, except for Open Access articles. (2024) Vol. 19, No 3

1. Introduction In order to support their life cycle, living organisms in an active state have to produce energy. The rate of energy production is called the metabolic rate. Metab- olism of living organisms can be de¯ned by emphasizing di®erent aspects of this complex phenomenon. For our purposes, the de¯nition in Webster’s Dictionary is an adequate one: \The chemical changes in living cells by which energy is provided for vital processes and activities and new material is assimilated to repair the waste." Metabolic rate generally increases slower than the mass of organisms.1–5 (In some instances although the reverse relationships were observed, like in the case of bac- terioplankton.6) This phenomenon is called metabolic allometric scaling. When it is considered across di®erent taxa, this is interspeci¯c allometric scaling (which is studied in this paper). When the same species are considered, the term intraspeci¯c allometric scaling is used. The fundamental causes of interspeci¯c allometric scaling are considered unknown. There are some credible hypotheses regarding the causes of intraspeci¯c allometric scaling. According to Ref. 7, it relates to cellular properties in°uenced by heat dissipation speci¯cs of organisms. This result is probably correct since other similar studies also point in the direction of cellular properties as key factors de¯ning intraspeci¯c allometric scaling. For instance, in Ref. 6, the authors acknowledge: \We have shown that cell size is a key functional trait in bacter- ioplankton communities." Despite the outer similarity of these two types of allo- metric scaling, the underlying mechanisms, de¯ning these two phenomena, are rather di®erent.7 This paper studies the metabolic allometric scaling of unicellular organisms. Al- lometric scaling of multicellular organisms was considered in a separate article,8 which should be read ¯rst. Both articles independently discover the same general principle in their respective domains that the origin of metabolic allometric scaling is a product of natural selection and optimization of nutrient distributio

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