On the nature of the earliest known lifeforms

Kanaparthi, Dheeraj; Lampe, Marko; Zhu, Bo; Boesen, Thomas; Klingl, Andreas; Schwille, Petra; Lueders, Tillmann

doi:10.1101/2021.08.16.456462

Cited by 3 publications

(11 citation statements)

References 118 publications

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“…Cells from our study bares remarkable morphological similarity with earliest known microfossils. Similar to what was observed in our study fossilized cells exhibited large intracellular vacuoles and internal daughter cells 60 . Extensive morphological comparison of microfossils with that of cells from our study, showed beyond a reasonable doubt that cells reproducing by the processes we described here, indeed existed on early Earth 60 .…”

Section: Resultssupporting

confidence: 91%

“…Moreover, elemental and isotopic signature of these microfossils suggest that these fossilized cells were metabolically active 15,61 . Spatial differences in the carbon isotope composition in these fossilized cells suggest that their cell membranes exhibited lateral heterogenicities 62,60 . Given these similarities between our results and microfossils, both of which being in agreement with that of top-down 54 and computational approaches 55 , we propose that protocells reproduced by a process similar to what we described here.…”

Section: Resultsmentioning

confidence: 99%

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The reproduction process of Gram-positive protocells

Kanaparthi¹,

Lampe²,

Hildebrand³

et al. 2021

Preprint

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Bacterial protoplasts are believed to reproduce in a haphazard manner. Their unregulated method of reproduction is considered the simplest of all known forms of cell replication. In the present study, we attempted to understand the evolutionary significance and physiochemical mechanisms behind this process. Here we transformed a Gram-positive bacterium into sack of cytoplasm, incapable of regulating either its morphology or reproductive processes. As such primitive (proto)cells devoid of molecular biological processes could have been native to early Earth, we grew these cells under environmental conditions of early Earth. We then monitored these cells at regular intervals to understand if they can grow and reproduce under these conditions. In our incubations, cells exhibited a multi-stage reproductive cycle resulting in viable daughter cells. What was previously thought to be a chaotic reproductive process, could in fact be well explained from a physicochemical perspective. Both morphology and reproductive process of these cells were determined by chemical and self-assembling properties of their cell constituents rather than the information encoded in their genome. Despite its haphazard appearance, we propose that the reproductive process of bacterial protoplasts is better optimized for environmental conditions of early Earth and could be reminiscent of protocell reproductive processes.Abstract Figure

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Section: Resultssupporting

confidence: 91%

Section: Resultsmentioning

confidence: 99%

The reproduction process of Gram-positive protocells

Kanaparthi¹,

Lampe²,

Hildebrand³

et al. 2021

Preprint

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“…However, no direct proof exists to conclusively state that protocells inhibiting early Earth did in fact reproduced by this process. To verify the validity of our proposition that protocells reproduced by these processes, we compared very distinctive RS-P morphologies observed in our study with the oldest known microfossils from 3.8-billion-year-old rock formations 48 . An extensive comparison of the cell morphologies, and elemental and isotopic composition of these microfossils is beyond the scope of the current study and is presented as an accompanying manuscript 48 .…”

Section: Discussionmentioning

confidence: 62%

“…Given the simplicity and efficiency with which cells reproduced under environmental conditions of early Earth, we propose that primitive protocells inhabiting early Earth could have reproduced in a similar way. In our subsequent work, we were able to demonstrate from the fossil record that cells reproducing by the above described processes in-deed existed on early Earth 40 .…”

Section: Discussionmentioning

confidence: 80%

The reproduction of Gram-negative protoplasts and the influence of environmental conditions on this process

Kanaparthi

Lampe

Zhu

et al. 2021

Preprint

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Protocells are thought to have existed on early Earth before the origin of prokaryotes. These primitive cells are believed to have carried out processes like replication solely based on the physicochemical properties of their cell constituents. Despite considerable efforts, replication of a living cell-driven entirely by laws of physics and chemistry has never been achieved. To test this hypothesis, we transformed extant bacteria into sacks of cytoplasm, incapable of regulating either their morphology or reproductive processes. We then exposed these proxy-protocells (bacterial protoplasts) to presumed Archaean Eon environmental conditions to understand if or how these cells reproduce. Contrary to the current presumption that bacterial protoplasts reproduce in a haphazard manner, under our experimental conditions they reproduced via a multi-stage reproductive cycle, resulting in viable daughter cells. Our observations suggest that this mechanism of reproduction could in fact be well explained from a biophysical perspective. Based on our observations we argue that this method of reproduction is better suited for the environmental conditions of early Earth.Graphical abstract

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“…A recent study reports similarities between spherical microfossils and wall-less protoplasts 66 . When protoplasts were grown in conditions that mimic the presumed conditions of the Archean Eon, the period when life formed on Earth, intracellular vesicles were formed.…”

Section: Discussionmentioning

confidence: 95%

Endocytosis-like DNA uptake by cell wall-deficient bacteria

et al. 2022

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Horizontal gene transfer in bacteria is widely believed to occur via conjugation, transduction and transformation. These mechanisms facilitate the passage of DNA across the protective cell wall using sophisticated machinery. Here, we report that cell wall-deficient bacteria can engulf DNA and other extracellular material via an endocytosis-like process. Specifically, we show that L-forms of the filamentous actinomycete Kitasatospora viridifaciens can take up plasmid DNA, polysaccharides (dextran) and 150-nm lipid nanoparticles. The process involves invagination of the cytoplasmic membrane, leading to formation of intracellular vesicles that encapsulate extracellular material. DNA uptake is not affected by deletion of genes homologous to comEC and comEA, which are required for natural transformation in other species. However, uptake is inhibited by sodium azide or incubation at 4 °C, suggesting the process is energy-dependent. The encapsulated materials are released into the cytoplasm upon degradation of the vesicle membrane. Given that cell wall-deficient bacteria are considered a model for early life forms, our work reveals a possible mechanism for primordial cells to acquire food or genetic material before invention of the bacterial cell wall.

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On the nature of the earliest known lifeforms

Cited by 3 publications

References 118 publications

The reproduction process of Gram-positive protocells

The reproduction process of Gram-positive protocells

The reproduction of Gram-negative protoplasts and the influence of environmental conditions on this process

Endocytosis-like DNA uptake by cell wall-deficient bacteria

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