China
Africa
Explore chapters and articles related to this topic
Introduction to Cells, DNA, and Viruses
Published in Patricia G. Melloy, Viruses and Society, 2023
Our focus will be on eukaryotes, which are cells (including our cells) containing a nucleus and other organelles. However, viruses can also infect prokaryotes. The most well-known prokaryotes are bacteria. Prokaryotes lack a nucleus and membrane-bound organelles (Alberts et al. 2019). There are two prokaryotic kingdoms: Archaea and Eubacteria. Archaea includes microorganisms (or microscopic organisms) that can live in extreme environments on the planet. Eubacteria includes microorganisms also known as bacteria and cyanobacteria (Minkoff and Baker 2004d).
Bacteria
Published in Julius P. Kreier, Infection, Resistance, and Immunity, 2022
Prokaryotic cells are fundamentally different from eukaryotic cells (Table 15.2). Structure is an important consideration because of the involvement of several structural components as factors of virulence, i.e., the ability of the microbe to cause disease. Figure 15.2 is an idealized schematic drawing of a prokaryotic cell showing structural components. It must be emphasized, however, that not all of the components shown are always present in a single species of bacteria. Keep in mind that all bacterial diseases are interactions between prokaryotic and eukaryotic cells.
Cancer Biology and Genetics for Non-Biologists
Published in Trevor F. Cox, Medical Statistics for Cancer Studies, 2022
All living things are made up of cells, from the simple unicellular amoeba to the complex human composed of about 37 trillion () cells. Cells that contain a nucleus are called eukaryotic cells; cells without a nucleus are called prokaryotic cells. Bacteria are examples of prokaryotic cells. Humans are eukaryotes consisting of eukaryotic cells, such as bone, nerve and stem cells. In fact, there are about 200 types of cells in our bodies. Figure 2.1 shows a typical eukaryotic cell, illustrating its structure. Cells come in different shapes and sizes; neurons in the brain and nervous system are long and thin, blood cells are roughly spherical, some bone cells are cuboidal and columnar while others have many branches. The size of a red blood cell is , the size of a skin cell is , an ovum , whilst the length of some nerve cells can be over .
Unblinding the watchmaker: cancer treatment and drug design in the face of evolutionary pressure
Published in Expert Opinion on Drug Discovery, 2022
Sophia Konig, Hannah Strobel, Michael Grunert, Marcin Lyszkiewicz, Oliver Brühl, Georg Karpel-Massler, Natalia Ziętara, Katia La Ferla-Brühl, Markus D. Siegelin, Klaus-Michael Debatin, Mike-Andrew Westhoff
The significance of resistance evolution shows the need to investigate large scale evolutionary dynamics; here, bacteria represent a good model system due to their brief generation time. For example, an experiment lasting eight days will result, assuming a generation time of 20 minutes, in (24 x 8 × 3 =) 576 generations. A similar experiment using cancer cell lines would take around two years (assuming an average population doubling time of 30 hours, i.e. 576 × 30 = 17,280 hours, i.e. 1.97 years). In a mouse system (assuming 11 weeks per generation) this would take 111 years and observing that many generations in humans (rather optimistically assuming 20 years per generation) would take 11,520 years. Importantly, prokaryotes have a distinct chromosomal organization and intrinsic natural genetic engineering capacities [88]; hence, the comparison between bacterial and cancer cell evolution should remain at the level of population dynamics and countermeasures to resistance development, not necessarily on molecular details. However, similar molecular strategies, for example, regarding stress-induced mutagenesis, i.e. the switch to polymerases with reduced proofreading capacities, have been observed in both cellular systems [89]. Indeed, since first general conclusions for the emergence of resistance were drawn from experiments with bacteria [90], more studies transferred what was seen in bacterial population dynamics to cancer [91–94].
An overview of sex and reproductive immunity from an evolutionary/anthropological perspective
Published in Immunological Medicine, 2021
Yoshihiko Araki, Hiroshi Yoshitake, Kenji Yamatoya, Hiroshi Fujiwara
Nevertheless, life on Earth must coexist with viruses, such as SERS-CoV-2, the cause of the recent pandemic [42]. Viruses may be at odds with life and are clearly not mutually beneficial. This can be said to be an everyday phenomenon in terms of the geological time scale. Before the emergence of sex, eukaryotic cells developed via symbiotic relationships with prokaryotes that became intracellular organelles, according to the endosymbiotic theory [43–45]. Specifically, mitochondria and chloroplasts were derived from aerobic bacteria and cyanobacteria, respectively. Eukaryotes, such as plants and animals, then evolved to undergo sexual reproduction. Furthermore, mammals developed a reproductive strategy that exploits the immune system by acquiring an unusual organ called the placenta, which is possibly the result of a virus being lodged in a mammalian ancestor. What is the destination of human prosperity and evolution through sexual reproduction? If we consider these issues from the perspective of both human cultural and biological histories, we may be able to see a slightly different side to the common sense of the past.
Gene editing technology: Towards precision medicine in inherited retinal diseases
Published in Seminars in Ophthalmology, 2021
Brian G. Ballios, Eric A. Pierce, Rachel M. Huckfeldt
In the late 1980s, it was discovered that the E. coli genome harbored clustered regularly interspaced short palindromic repeats (CRISPR), 81 which were later found to harbor sequences that match viral genomes.82,83 CRISPR-associated (Cas) proteins were discovered that can capture or cleave, and inactivate, the genome of invading viruses, guided by short RNA (crRNA) sequences84 coupled with trans-acting RNA (tracrRNA) that participates in processing and cleavage of the invading DNA.85 CRISPR gives these prokaryotes the ability to recognize the genetic sequence of an invading DNA-virus and target it for destruction. This constitutes what can be imagined as a prokaryote “immune system” to defend against infection from invading viruses. These three components (Cas, crRNA, and tracrRNA) form the basic structure of the endonuclease that is now used for gene editing,86 and it was not long after its discovery that it was shown that modified CRISPR-Cas9 could be used to make targeted edits in the mouse and human genome.87