An Overview of Parasite Diversity
Eric S. Loker, Bruce V. Hofkin in Parasitology, 2015
Many of these topics will be revisited throughout the book, but in this chapter we first provide an overview of the immense diversity of parasites using evolutionary trees as a framework to portray this diversity. As part of this overview, we include discussion of horizontal gene transfer (HGT), a process in which one organism acquires genetic information from another organism without being the offspring of that organism. Thereafter, examples are provided that show how the evolutionary relationships of some enigmatic parasite groups have been revealed, while noting that others still defy resolution. Also discussed are examples of how humans have acquired some of our parasites and how we can retrace their evolutionary histories. The search for new parasite diversity is ongoing and some examples of how this search is undertaken and the diversity cataloged are described in Box 2.1. We also discuss some examples of improved classification schemes that are based on a thorough knowledge of parasite diversity and evolutionary relationships.
Psychosis and stories
Alex Jelly, Adel Helmy, Barbara A. Wilson in Life After a Rare Brain Tumour and Supplementary Motor Area Syndrome, 2019
Looking across at the patient opposite, and seeing her reading something behind my bed, scanning and then, as I looked at her, pretending not to. What was she looking at? Of course! Her bacteria were learning the language of humans.“Please turn me.”“No thank you, I won’t have any antibiotics.”“May I have a lollipop, please?” They’re so much more sophisticated than their hosts. They were here first, creating life from chemical vents under the ocean. They specialise in horizontal gene transfer. They’ve hitched lifts to the moon. They live off and with hosts so numerous and diverse that their survival is guaranteed. Being able to morph into any form, travelling on clouds. Being able to withstand radioactivity far greater than anything found on Earth. (And why is that? They must have grand plans!)
Basic Microbiology
Philip A. Geis in Cosmetic Microbiology, 2020
Unlike eukaryotic cells, bacteria can transfer DNA sequences between individuals that are not of the same lineage. This can occur between members of the same species or between different species. The three main mechanisms that bacteria use to perform horizontal gene transfer are listed here. Transformation—DNA found within the extracellular environment of the bacteria is actively taken up into the bacteria and is used either in its native state, such as with plasmids, or incorporated into the genome, as with chromosomal DNA sequences. The utilization of these sequences can often confer drastic new phenotypes on the bacteria that harbor those sequences.Transduction—Viruses that are present, incorporated into the chromosome of a bacterium, exit the infected bacteria to infect new host cells. In the process, they remove small portions of the chromosome of the infected bacteria. In the new host, these sequences are integrated into the new host genome.Conjugation—As mentioned previously, bacteria that are able to conjugate by producing sex pili can transfer DNA sequences across the pili and lead to incorporation of new chromosomal sequences within the other mating bacteria.
The war against bacteria, from the past to present and beyond
Published in Expert Review of Anti-infective Therapy, 2022
Lucrezia Bottalico, Ioannis Alexandros Charitos, Maria Assunta Potenza, Monica Montagnani, Luigi Santacroce
While in several cases described above bacterial resistance is acquired to one or at most two groups of antimicrobials, which are usually chemically related, in some other cases multi-drug resistant strains are created, making them particularly difficult to treat [2]. Among the defensive modalities reported by bacteria, some differences in the function of the bacterial cell may result in the acquisition of resistance to few antibiotics and/or multi-resistance to several classes of distinct antibiotics. As mentioned, there are basically two ways of occurrence: a) mutagenesis, although this is a less frequent mechanism b) horizontal transfer of genetic material (HGT, Horizontal Gene Transfer). In this last case, genes of the host bacterium may undergo a spontaneous mutation, or genes may belong to bacteria producing the same antibiotic substances and therefore they have self-defense mechanisms, or finally genes may belong to soil bacteria possessing inherited resistance [2,131–135]. Resistance mechanisms may depend on mutations in bacterial chromosomal genes encoding antibiotic susceptibility, or on the transfer of extrachromosomal elements, such as plasmids, integrons, and transposons. Data can be transferred between bacteria via conjugation (cell-to-cell contact), transduction (bacteriophage insertion), or transformation (naked DNA uptake). Transfer of genes occurs when bacterial cells are near (as in the intestinal tract, in starter cultures, in fermented foods, etc.) [2].
Circumventing antimicrobial-resistance and preventing its development in novel, bacterial infection-control strategies
Published in Expert Opinion on Drug Delivery, 2020
Tianrong Yu, Guimei Jiang, Ruifang Gao, Gaojian Chen, Yijin Ren, Jian Liu, Henny C. van der Mei, Henk J. Busscher
Persisters can comprise 1% of a biofilm-population [84] but due to their antibiotic-tolerance often related to chronic infections as they can start re-growing when antibiotic pressure is relieved. Antibiotic-resistant bacteria have genetically changed to block antibiotic activity and grow in the presence of antibiotics. Typically, a biofilm houses subpopulations of bacteria that are susceptible and resistant to an antibiotic, a phenomenon called hetero-resistance [85,86]. Accordingly, the crowdedness and close proximity between bacteria in a biofilm-mode of growth create a hot-spot for horizontal gene transfer occurring within and between bacterial species and resulting genetic changes [87]. Horizontal gene transfer requires a membrane-associated DNA transport system as a part of natural, bacterial evolution [88]. Antibiotic-resistant mutants therefore generally appear more frequent in bacteria in a biofilm-mode of growth than during planktonic growth and accordingly inhibitory (MIC) and bactericidal concentrations (MBC), against biofilm bacteria, are much higher than that of planktonic bacteria [89,90].
Conditioning of metal surfaces enhances Shewanella chilikensis adhesion
Published in Biofouling, 2022
Benjamin Tuck, Elizabeth Watkin, Anthony Somers, Maria Forsyth, Laura L. Machuca
Once adsorbed to metal structures, it remains unclear how amino acids and eDNA will affect bacterial attachment. Both organic compounds provide numerous benefits to bacteria, and were therefore hypothesised to elicit a positive effect on attachment. DNA for example acts as a platform for horizontal gene transfer (Draghi and Turner 2006), which can boost chemical and environmental tolerance through the incorporation of new genes (Ibáñez de Aldecoa et al. 2017). Amino acids have been demonstrated to be effective chemotactic agents, actively attracting motile bacteria (Yang et al. 2015). Further, both amino acids and eDNA represent organic carbon sources utilised by bacterial metabolisms (Jørgensen et al. 1993). Based on this research, it was hypothesised in the present study that these molecules at the CS interface would result in enhanced surface colonisation compared with surfaces not pre-conditioned with these molecules.
Related Knowledge Centers
- Antimicrobial Resistance
- Bacteria
- Bacteriophage
- DNA
- Transduction
- Virulence
- Reproduction
- Temperateness
- Plasmid
- Transformation