Bacterial Colonization
Bacterial colonization refers to the process by which bacteria establish and multiply in a particular environment, such as the human body or a surface. This process involves the initial attachment of bacteria to a substrate, followed by growth and formation of a stable community. Bacterial colonization can have both beneficial and harmful effects, depending on the specific bacteria involved and the host environment.
4 Key excerpts on "Bacterial Colonization"
eBook - ePub- Britannica Educational Publishing, Kara Rogers(Authors)
- 2010(Publication Date)
- Britannica Educational Publishing(Publisher)
...CHAPTER 2 Growth, Ecology, and Evolution of Bacteria T he ability of bacteria to thrive in specific habitats, such as the human intestine or forest soil, is a function of both nutritional and physical factors. Each type of bacteria has specific growth requirements, which may be decided by an organism’s ability to metabolize only one kind of carbohydrate or to tolerate only certain pH levels and temperatures. Thus, the relationship between bacteria and the environment, as well as between bacteria and plants, animals, and other organisms, is a reflection of their specific growth requirements. These specifications are in turn the product of millions of years of evolution and adaptation. BIOSYNTHESIS, NUTRITION, AND GROWTH OF BACTERIA The growth of bacterial populations is dependent on both the extent of nutrients available in a given environment and the various growth requirements of the organisms. Bacterial growth rates are highly variable. Division cycles and population doubling for some species may take only minutes, whereas for others these processes may take days. Growth rates and the limitations imposed by nutrient availability and metabolic requirements have been studied extensively in the laboratory. As a result, there exists a large body of knowledge concerning the various metabolic pathways utilized by different organisms, which has enabled microbiologists to calculate and predict the generation times for specific types of bacteria under all sorts of growth conditions. G ROWTH OF B ACTERIAL P OPULATIONS Growth of bacterial cultures is defined as an increase in the number of bacteria in a population rather than in the size of individual cells. The growth of a bacterial population occurs in a geometric or exponential manner: with each division cycle (generation), one cell gives rise to 2 cells, then 4 cells, then 8 cells, then 16, then 32, and so forth...
eBook - ePubNutrition and Development
Short and Long Term Consequences for Health
- Thomas A. B. Sanders, Sara Stanner(Authors)
- 2013(Publication Date)
- Wiley-Blackwell(Publisher)
...7 Establishing of Gut Microbiota and Bacterial Colonisation of the Gut in Early Life 7.1 Introduction Once considered to merely be a waste disposal system with efficient water absorption capabilities, the human colon is now recognised to be one of the most metabolically active systems in the human body. This is thanks to the actions of the colonic microbiota, which make up the greatest proportion of the human gastrointestinal (GI) or gut microbiota – a complex microbial community comprising millions and millions of bacterial cells (>10 12). Indeed, the human body contains more bacterial cells (numerically at least) than human cells, although in mass we are more human than bacterial. We not only play host to this extensive bacterial population, but (as with any ecosystem) we have evolved together with our microbial inhabitants and our health and well-being can be affected (positively or negatively) by the actions of the gut microbiota (as a whole and by individual members). The acquisition of gut microbiota is essential, as they provide colonisation resistance (occupying adhesion sites and utilising nutrients available in the intestines or by altering the environment), thereby reducing opportunity for colonisation by harmful microorganisms; scavenge energy and enhance the bioavailability of certain nutrients and minerals for the host; stimulate epithelial development and maturation of the immune system. Certain bacterial populations added in the diet as probiotics such as Bifidobacterium breve and Lactobacillus rhamnosus (administered maternally [during pregnancy and/or breastfeeding] or during early infancy in formula milk) have also been shown to reduce the risk of developing asthma, atopic dermatitis and other common allergies in childhood. However, certain patterns of colonisation, predominantly aerobic Gram-negative bacteria are thought to play a role in severe disorders such as necrotising enterocolitis, frequently observed in pre-term infants...
eBook - ePubThe Human Microbiota in Health and Disease
An Ecological and Community-based Approach
- Mike Wilson(Author)
- 2018(Publication Date)
- Garland Science(Publisher)
...Further growth may then take place resulting in the production of a biofilm (Figure 2.9). Figure 2.9. The various patterns of microbial colonization that may be found on host tissues. A microbe may adhere to a substratum but may not be able to grow and reproduce there because of inappropriate environmental conditions. However, it may remain viable. If conditions are suitable for its growth it may reproduce and form a microcolony consisting of a number of microbes enclosed within a matrix of extracellular microbial polymers. A microcolony may eventually be able to grow into a larger structure known as a biofilm. Within this biofilm conditions may be suitable for the growth of other microbes resulting in the formation of a community consisting of several species. Microbes may also reside within epithelial cells. The different colors represent different microbial species. A microcolony is an adherent microbial aggregate which is often enclosed within a polymeric coating secreted by the organism (see Figure 2.9). Microcolonies arise from the growth and reproduction of a single parent cell and, consequently, consist of only one type of microbe. They have been detected at numerous body sites and Figure 2.10 shows microcolonies on the surface of the skin and on the rectal mucosa. Figure 2.10. Microcolonies on the surface of the skin and on the rectal mucosa. (A–C) Scanning electron micrographs of a bacterial colony on the surface of the arm. Panels B and C show the microcolony arrowed in (A) at increasing magnifications. (D) Photomicrograph showing a microcolony on the rectal mucosa. The bacteria are stained with a live/dead stain—live cells are colored yellow while dead cells are red. ([A–C] Reprinted from J Dermatol Sci, 38, Katsuyama M et al., 197–205, Copyright 2005 with permission from Elsevier; [D] From Wilson M & Devine D (2003)...
eBook - ePubBacterial Pathogenesis
A Molecular Approach
- Brenda A. Wilson, Malcolm Winkler, Brian T. Ho(Authors)
- 2019(Publication Date)
- ASM Press(Publisher)
...An interesting aspect of this protozoal grazing that has attracted particular attention recently is that protozoa have properties that are remarkably similar to human phagocytic cells, cells that form an important part of the defenses of the human body. Some of these human phagocytic cells function mainly to engulf, break down, and clear bacteria in blood and tissues. Of these, some then present components of broken-down bacteria to the cells of the immune system. When animals and humans finally appeared on the evolutionary scene, bacteria immediately took advantage of them as rich niches in which to grow. To a bacterium accustomed to the vagaries of the external environment, where ambient temperature and availability of water and nutrients can vary widely (and unpredictably), a warm-blooded animal whose body temperature is stably maintained and whose lifestyle involves constantly collecting food and water from the environment must be as close as it gets to bacterial heaven. As such, it should not be surprising that the bodies of humans and animals carry dense bacterial loads, especially in the mouth, intestinal tract, and vaginal tract. Small wonder that the human or animal body is often referred to in the scientific literature as the host and that the interaction between a bacterium and its host is referred to as a host-microbe relationship. Until recently, scientists studying the evolution of insects, animals, and humans almost completely ignored the selective pressure exerted by the long-term presence of the large and diverse populations of bacteria with their hosts. Now, a rapidly expanding area of research has emerged that is devoted to studying the coevolution of hosts with their resident microbial communities, also known as microbiomes. As will become evident in the next few chapters, the effects of microbial pressure can be seen clearly in the design of human skin, eyes, lungs, intestinal tract, vaginal tract, and in particular the immune system...
