Biology subjects

Lueders, T.

Publications and source records attributed to Lueders, T..

5 recordsLinked to original sources

bioRxiv2024

On the annotation of Paleo- and Mesoproterozoic microfossils as fungi

How old is the crown group Fungi? Inferences from phylogenetic and fossil-based studies provided far-apart age estimates ranging between 0.75 to 2.7 billion years old. One important criterion for interpreting Paleo- and Mesoproterozoic microfossils as Fungi is their uncanny morphological resemblance with extant fungi. Here, we demonstrate that bacteria exposed to environmental conditions similar to the paleoenvironmental settings where these presumed fungi lived can spontaneously transform into their protoplasts. These protoplasts exhibit morphologies corresponding to those of presumed fungal microfossils. These observations, together with microfossil chemical composition, pose a serious challenge to interpreting Paleo- and Mesoproterozoic microfossils as fungi. Based on these results, we reiterate that morphology is not a reliable indicator of the phylogeny of microfossils older than 2.5Ga.

evolutionary biology↗

bioRxiv2021

On the reproductive mechanism of Gram-negative protocells

Bacterial protoplasts are known to reproduce independently of canonical molecular biological processes. Their reproduction is shown to be mediated entirely by the physicochemical properties of cell constituents. However, the physiochemical properties of the cell constituents are influenced by the environmental conditions like salinity, salt composition, and mechanical stresses experienced by a cell in natural environments. The influence of such environmental conditions on protoplast reproduction is seldom investigated. Here, we studied protoplast reproduction in their native environmental conditions. Contrary to the previous perceptions of protoplasts reproducing in an erratic manner, cells in our study reproduced in a defined sequence of steps. The process of their reproduction can be explained by an interplay between intracellular metabolism, the physicochemical properties of cell constituents, and the nature of cations in the growth media. We observed a minimal leakage of intracellular constituents during protoplast reproduction, suggesting an efficient reproduction. However, the efficiency of reproduction is determined by the environmental conditions. Under favorable environmental conditions, protoplasts reproduce with nearly similar efficiency to cells that possess a cell wall. In short, here we demonstrate the simplest method of cellular reproduction and the influence of environmental conditions on this process.

biophysics↗

bioRxiv2021

On the reproductive mechanisms of Gram-positive protocells

Prokaryotes are hypothesized to have evolved from more primitive protocells. Unlike present-day cells, protocells are thought to have been devoid of complex molecular biological processes. They are believed to have mediated reproduction entirely by biophysical forces under favorable environmental conditions. Despite this proposition, little is known about the actual mechanism of their reproduction. To understand the reproduction process of protocells in their native habitat, here we used a top-down approach to transform bacterial cells into a primitive lipid vesicle-like state. Given that environmental conditions are thought to have played an essential role in mediating protocell reproduction, we then studied these cells under the presumed environmental conditions of Archaean Eon Earth. Even in the absence of functioning biological processes, cells in our study reproduced in a defined sequence of steps, always leading to the formation of viable daughter cells. Their reproduction mechanism can be explained by the interaction between intracellular metabolism, physicochemical properties of cell constituents, and, most importantly, environmental conditions. Given the simplicity of this reproduction mechanism and its suitability to environmental conditions of early Earth, we propose that protocells reproduced by this process. Moreover, this method of reproduction is also in tune with the earlier theoretical propositions on protocells, the results of the top- down approach of building a minimal cell, and the paleontological record of the Achaean Eon. Our study is the first to bridge the gap between non-living systems like lipid vesicles, living cells, and the paleontology of the Archaean Eon.

biophysics↗

bioRxiv2021

On the nature of the earliest known life forms

Microfossils from the Paleoarchean Eon are the oldest known evidence of life. Despite their significance in understanding the history of life on Earth, any interpretation of the nature of these microfossils has been a point of contention among researchers. Decades of back-and-forth arguments led to the consensus that reconstructing the lifecycles of Archaean Eon organisms is the most promising way of understanding the nature of these microfossils. Here, we transformed a Gram-positive bacterium into a primitive lipid vesicle-like state and studied it under environmental conditions prevalent on early Earth. Using this approach, we successfully reconstructed morphologies and life cycles of Archaean microfossils. In addition to reproducing microfossil morphologies, we conducted experiments that spanned years to understand the process of cell degradation and how Archaean cells could have undergone encrustation minerals (in this case, salt), leading to their preservation as fossilized organic carbon in the rock record. These degradation products strongly resemble fossiliferous features from Archaean rock formations. Our observations suggest that microfossils aged between 3.8 to 2.5Ga most likely were liposome-like protocells that have evolved physiological pathways of energy conservation but not the mechanisms to regulate their morphology. Based on these observations, we propose that morphology is not a reliable indicator of taxonomy in these microfossils.

evolutionary biology↗

bioRxiv2019

Tissue- and population-level microbiome analysis of the wasp spider Argiope bruennichi identifies a novel dominant bacterial symbiont

Many ecological and evolutionary processes in animals depend upon microbial symbioses. In spiders, the role of the microbiome in these processes remains mostly unknown. We compared the microbiome between populations, individuals, and tissue types of a range-expanding spider, using 16S rRNA gene sequencing. Our study is one of the first to go beyond targeting known endosymbionts in spiders, and characterizes the total microbiome across different body compartments (leg, prosoma, hemolymph, book lungs, ovaries, silk glands, midgut, and fecal pellets). Overall, the microbiome differs significantly between populations and individuals, but not between tissue types. The microbiome of the wasp spider Argiope bruennichi features a novel dominant bacterial symbiont, which is abundant in every tissue type in spiders from geographically distinct populations, and present in offspring. The novel symbiont is affiliated with the Tenericutes, but has low sequence identity (<85%) to all previously named taxa, suggesting that the novel symbiont represents a new bacterial clade. Its presence in offspring implies that it is vertically transmitted. Our results shed light on the processes which shape microbiome differentiation in this species, and raise several questions about the implications of the novel dominant bacterial symbiont on the biology and evolution of its host.

microbiology↗