Phenotypic Heterogeneity and the Evolution of Bacterial Life Cycles

Most bacteria live in colonies, where they often express different cell types. The ecological significance of these cell types and their evolutionary origin are often unknown. Here, we study the evolution of cell differentiation in the context of surface colonization. We particularly focus on the evolution of a ‘sticky’ cell type that is required for surface attachment, but is costly to express. The sticky cells not only facilitate their own attachment, but also that of non-sticky cells. Using individual-based simulations, we show that surface colonization rapidly evolves and in most cases leads to phenotypic heterogeneity, in which sticky and non-sticky cells occur side by side on the surface. In the presence of regulation, cell differentiation leads to a remarkable set of bacterial life cycles, in which cells alternate between living in the liquid and living on the surface. The dominant life stage is formed by the surface-attached colony that shows many complex features: colonies reproduce via fission and by producing migratory propagules; cells inside the colony divide labour; and colonies can produce filaments to facilitate expansion. Overall, our model illustrates how the evolution of an adhesive cell type goes hand in hand with the evolution of complex bacterial life cycles

A glimpse into daily life in an Ottoman harbour: Evidence from a cesspit in Ainos (Türkiye)

The daily life of non-elite people from the past is usually hard to evaluate, since historical sources largely concentrate on the upper classes. This knowledge can be gained by archaeological excavations and use of geo- and bioarchaeological methods. In 2021, geophysical prospections in Enez (Türkiye) revealed a circular stone structure. The excavators identified a latrine probably used from 17th until the 19th century. Palynological, palaeoparasitological and archaeobotanical methods have been applied for understanding the diet, hygiene and diseases of the people using the latrine. The cesspit was a closed round structure with walls made of stones. It had no contamination from outside and was filled with liquid or semi-liquid content with dissolved salts and organic matter derived from urine, faeces, kitchen waste, dung and other rubbish. Results show a broad diet including wheat, chili peppers, olives, spices, a wide range of fruits, meat, fish and oysters. This sanitation did not protect the inhabitants of the house from intestinal parasites in the forms of helminths whipworm, roundworm and the protozoan Giardia duodenalis that causes diarrhoea. The data highlight the special role played by the harbour of Ainos in the establishment and possible expansion of new food products from the New World

Thelytokous parthenogenesis and its consequences on inbreeding in an ant

Thelytokous parthenogenesis, that is, the production of diploid daughters from unfertilized eggs, may involve various cytological mechanisms, each having a different impact on the genetic structure of populations. Here, we determined the cytological mechanism of thelytokous parthenogenesis and its impact on inbreeding in the ant Cataglyphis cursor, a species where queens use both sexual and asexual reproduction to produce, respectively, workers and new queens. It has been suggested that thelytokous parthenogenesis in C. cursor might have been selected for to face high queen mortality and, originally, to allow workers to replace the queen when she passes away. We first determined the mode of thelytokous parthenogenesis by comparing the rate of transition to homozygosity at four highly polymorphic loci to expectations under the different modes of parthenogenesis. Our data show that thelytoky is achieved through automictic parthenogenesis with central fusion. We then estimated the proportion of colonies headed by worker-produced queens in a natural population. We designed a model linking the observed homozygosity in queens to the proportion of queens produced by workers, based on the assumption that (i) parthenogenesis is automictic with central fusion and (ii) queen lineage is asexually produced, resulting in an increase of the inbreeding over generations, whereas workers are sexually produced and therefore not inbred. Our results indicate that more than 60% of the colonies should be headed by a worker-produced queen, suggesting that queen's lifespan is low in this species.Journal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe