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Reber AS, Baluška F, Miller WB, Slijepčević P. The sensual cell: Feeling and affect in unicellular species. Biosystems 2024; 238:105197. [PMID: 38556108 DOI: 10.1016/j.biosystems.2024.105197] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2024] [Revised: 03/21/2024] [Accepted: 03/22/2024] [Indexed: 04/02/2024]
Abstract
Our previous efforts to probe the complex, rich experiential lives of unicellular species have focused on the origins of consciousness (Reber, 2019) and the biomolecular processes that underlie sentience (Reber et al., 2023). Implied, but unexplored, was the assumption that these cognitive functions and associated unicellular organismal behaviors were linked with and often driven by affect, feelings, sensual experiences. In this essay we dig more deeply into these valenced (We're using the term valence here to cover the aspects of sensory experiences that have evaluative elements, are experienced as positive or negative ─ those where this affective, internal representation is an essential element in how the input is interpreted and responded to.) self-referencing features. In the first part, we examine the empirical evidence for various sensual experiences that have been identified. In the second part, we look at other features of prokaryote life that appear to also have affective, valenced elements but where the data to support the proposition aren't as strong. We engage in some informed speculation about these phenomena.
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Affiliation(s)
- Arthur S Reber
- Department of Psychology, University of British Columbia, Vancouver, BC, Canada.
| | - František Baluška
- Institute of Cellular and Molecular Botany, University of Bonn, Germany.
| | | | - Predrag Slijepčević
- Department of Life Sciences, College of Health, Medicine and Life Sciences, University of Brunel, UK.
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2
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Larson BT. Perspectives on Principles of Cellular Behavior from the Biophysics of Protists. Integr Comp Biol 2023; 63:1405-1421. [PMID: 37496203 PMCID: PMC10755178 DOI: 10.1093/icb/icad106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Revised: 07/14/2023] [Accepted: 07/17/2023] [Indexed: 07/28/2023] Open
Abstract
Cells are the fundamental unit of biological organization. Although it may be easy to think of them as little more than the simple building blocks of complex organisms such as animals, single cells are capable of behaviors of remarkable apparent sophistication. This is abundantly clear when considering the diversity of form and function among the microbial eukaryotes, the protists. How might we navigate this diversity in the search for general principles of cellular behavior? Here, we review cases in which the intensive study of protists from the perspective of cellular biophysics has driven insight into broad biological questions of morphogenesis, navigation and motility, and decision making. We argue that applying such approaches to questions of evolutionary cell biology presents rich, emerging opportunities. Integrating and expanding biophysical studies across protist diversity, exploiting the unique characteristics of each organism, will enrich our understanding of general underlying principles.
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Affiliation(s)
- Ben T Larson
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94158, USA
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Rajan D, Makushok T, Kalish A, Acuna L, Bonville A, Correa Almanza K, Garibay B, Tang E, Voss M, Lin A, Barlow K, Harrigan P, Slabodnick MM, Marshall WF. Single-cell analysis of habituation in Stentor coeruleus. Curr Biol 2023; 33:241-251.e4. [PMID: 36435177 PMCID: PMC9877177 DOI: 10.1016/j.cub.2022.11.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Revised: 09/26/2022] [Accepted: 11/03/2022] [Indexed: 11/26/2022]
Abstract
Although learning is often viewed as a unique feature of organisms with complex nervous systems, single-celled organisms also demonstrate basic forms of learning. The giant ciliate Stentor coeruleus responds to mechanical stimuli by contracting into a compact shape, presumably as a defense mechanism. When a Stentor cell is repeatedly stimulated at a constant level of force, it will learn to ignore that stimulus but will still respond to stronger stimuli. Prior studies of habituation in Stentor reported a graded response, suggesting that cells transition through a continuous range of response probabilities. By analyzing single cells using an automated apparatus to deliver calibrated stimuli, we find that habituation occurs via a single step-like switch in contraction probability within each cell, with the graded response in a population arising from the random distribution of switching times in individual cells. This step-like response allows Stentor behavior to be represented by a simple two-state model whose parameters can be estimated from experimental measurements. We find that transition rates depend on stimulus force and also on the time between stimuli. The ability to measure the behavior of the same cell to the same stimulus allowed us to quantify the functional heterogeneity among single cells. Together, our results suggest that the behavior of Stentor is governed by a two-state stochastic machine whose transition rates are sensitive to the time series properties of the input stimuli.
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Affiliation(s)
- Deepa Rajan
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, USA
| | - Tatyana Makushok
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, USA
| | - Asa Kalish
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, USA
| | - Lilibeth Acuna
- CCC Summer course, Center for Cellular Construction, San Francisco State University, San Francisco, CA, USA
| | - Alex Bonville
- CCC Summer course, Center for Cellular Construction, San Francisco State University, San Francisco, CA, USA
| | - Kathya Correa Almanza
- CCC Summer course, Center for Cellular Construction, San Francisco State University, San Francisco, CA, USA
| | - Brenda Garibay
- CCC Summer course, Center for Cellular Construction, San Francisco State University, San Francisco, CA, USA
| | - Eric Tang
- CCC Summer course, Center for Cellular Construction, San Francisco State University, San Francisco, CA, USA
| | - Megan Voss
- CCC Summer course, Center for Cellular Construction, San Francisco State University, San Francisco, CA, USA
| | - Athena Lin
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, USA
| | - Kyle Barlow
- Integrative Program in Quantitative Biology, University of California, San Francisco, San Francisco, CA, USA
| | - Patrick Harrigan
- Integrative Program in Quantitative Biology, University of California, San Francisco, San Francisco, CA, USA
| | - Mark M Slabodnick
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, USA
| | - Wallace F Marshall
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, USA.
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Echigoya S, Sato K, Kishida O, Nakagaki T, Nishigami Y. Switching of behavioral modes and their modulation by a geometrical cue in the ciliate Stentor coeruleus. Front Cell Dev Biol 2022; 10:1021469. [PMID: 36393838 PMCID: PMC9663998 DOI: 10.3389/fcell.2022.1021469] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Accepted: 10/17/2022] [Indexed: 08/14/2023] Open
Abstract
Protists ubiquitously live in nature and play key roles in the food web chain. Their habitats consist of various geometrical structures, such as porous media and rigid surfaces, affecting their motilities. A kind of protist, Stentor coeruleus, exhibits free swimming and adhering for feeding. Under environmental and culture conditions, these organisms are often found in sediments with complex geometries. The determination of anchoring location is essential for their lives. However, the factors that induce the behavioral transition from swimming to adhering are still unknown. In this study, we quantitatively characterized the behavioral transitions in S. coeruleus and observed the behavior in a chamber with dead ends made by a simple structure mimicking the environmental structures. As a result, the cell adheres and feeds in narrow spaces between the structure and the chamber wall. It may be reasonable for the organism to hide itself from predators and capture prey in these spaces. The behavioral strategy for the exploration and exploitation of spaces with a wide variety of geometries in their habitats is discussed.
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Affiliation(s)
- Syun Echigoya
- Graduate School of Life Science, Hokkaido University, Sapporo, Japan
| | - Katsuhiko Sato
- Graduate School of Life Science, Hokkaido University, Sapporo, Japan
- Research Institute for Electronic Science, Hokkaido University, Sapporo, Japan
| | - Osamu Kishida
- Field Science Center for Northern Biosphere, Tomakomai Experimental Forest, Hokkaido University, Tomakomai, Japan
| | - Toshiyuki Nakagaki
- Graduate School of Life Science, Hokkaido University, Sapporo, Japan
- Research Institute for Electronic Science, Hokkaido University, Sapporo, Japan
| | - Yukinori Nishigami
- Graduate School of Life Science, Hokkaido University, Sapporo, Japan
- Research Institute for Electronic Science, Hokkaido University, Sapporo, Japan
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Ohmura T, Nishigami Y, Ichikawa M. Simple dynamics underlying the survival behaviors of ciliates. Biophys Physicobiol 2022; 19:e190026. [PMID: 36160323 PMCID: PMC9465405 DOI: 10.2142/biophysico.bppb-v19.0026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Accepted: 08/05/2022] [Indexed: 12/01/2022] Open
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Timsit Y, Grégoire SP. Towards the Idea of Molecular Brains. Int J Mol Sci 2021; 22:ijms222111868. [PMID: 34769300 PMCID: PMC8584932 DOI: 10.3390/ijms222111868] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Revised: 10/24/2021] [Accepted: 10/28/2021] [Indexed: 02/06/2023] Open
Abstract
How can single cells without nervous systems perform complex behaviours such as habituation, associative learning and decision making, which are considered the hallmark of animals with a brain? Are there molecular systems that underlie cognitive properties equivalent to those of the brain? This review follows the development of the idea of molecular brains from Darwin’s “root brain hypothesis”, through bacterial chemotaxis, to the recent discovery of neuron-like r-protein networks in the ribosome. By combining a structural biology view with a Bayesian brain approach, this review explores the evolutionary labyrinth of information processing systems across scales. Ribosomal protein networks open a window into what were probably the earliest signalling systems to emerge before the radiation of the three kingdoms. While ribosomal networks are characterised by long-lasting interactions between their protein nodes, cell signalling networks are essentially based on transient interactions. As a corollary, while signals propagated in persistent networks may be ephemeral, networks whose interactions are transient constrain signals diffusing into the cytoplasm to be durable in time, such as post-translational modifications of proteins or second messenger synthesis. The duration and nature of the signals, in turn, implies different mechanisms for the integration of multiple signals and decision making. Evolution then reinvented networks with persistent interactions with the development of nervous systems in metazoans. Ribosomal protein networks and simple nervous systems display architectural and functional analogies whose comparison could suggest scale invariance in information processing. At the molecular level, the significant complexification of eukaryotic ribosomal protein networks is associated with a burst in the acquisition of new conserved aromatic amino acids. Knowing that aromatic residues play a critical role in allosteric receptors and channels, this observation suggests a general role of π systems and their interactions with charged amino acids in multiple signal integration and information processing. We think that these findings may provide the molecular basis for designing future computers with organic processors.
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Affiliation(s)
- Youri Timsit
- Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO UM110, 13288 Marseille, France
- Research Federation for the Study of Global Ocean Systems Ecology and Evolution, FR2022/Tara GOSEE, 3 rue Michel-Ange, 75016 Paris, France
- Correspondence:
| | - Sergeant-Perthuis Grégoire
- Institut de Mathématiques de Jussieu—Paris Rive Gauche (IMJ-PRG), UMR 7586, CNRS-Université Paris Diderot, 75013 Paris, France;
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Bioluminescence and Photoreception in Unicellular Organisms: Light-Signalling in a Bio-Communication Perspective. Int J Mol Sci 2021; 22:ijms222111311. [PMID: 34768741 PMCID: PMC8582858 DOI: 10.3390/ijms222111311] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Revised: 10/12/2021] [Accepted: 10/13/2021] [Indexed: 12/13/2022] Open
Abstract
Bioluminescence, the emission of light catalysed by luciferases, has evolved in many taxa from bacteria to vertebrates and is predominant in the marine environment. It is now well established that in animals possessing a nervous system capable of integrating light stimuli, bioluminescence triggers various behavioural responses and plays a role in intra- or interspecific visual communication. The function of light emission in unicellular organisms is less clear and it is currently thought that it has evolved in an ecological framework, to be perceived by visual animals. For example, while it is thought that bioluminescence allows bacteria to be ingested by zooplankton or fish, providing them with favourable conditions for growth and dispersal, the luminous flashes emitted by dinoflagellates may have evolved as an anti-predation system against copepods. In this short review, we re-examine this paradigm in light of recent findings in microorganism photoreception, signal integration and complex behaviours. Numerous studies show that on the one hand, bacteria and protists, whether autotrophs or heterotrophs, possess a variety of photoreceptors capable of perceiving and integrating light stimuli of different wavelengths. Single-cell light-perception produces responses ranging from phototaxis to more complex behaviours. On the other hand, there is growing evidence that unicellular prokaryotes and eukaryotes can perform complex tasks ranging from habituation and decision-making to associative learning, despite lacking a nervous system. Here, we focus our analysis on two taxa, bacteria and dinoflagellates, whose bioluminescence is well studied. We propose the hypothesis that similar to visual animals, the interplay between light-emission and reception could play multiple roles in intra- and interspecific communication and participate in complex behaviour in the unicellular world.
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