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Spread and Control of Microbes
Published in Jim Lynch, What Is Life and How Might It Be Sustained?, 2023
The discovery of microbes as animalcules by Antonie van Leeuwenhoek was made possible with the development of the microscope as was discussed in Chapter 2. These rod or spherical (coccus) forms were bacteria of around 1 μm in size. It took much longer with the development of the powerful electron microscope by Ernst Ruska in 1931 to visualise viruses which are often only about one-tenth the size of bacteria and are not cells but packages of nucleic acids (RNA or DNA), surrounded by a protective coat called a capsid. Some larger viruses can be as big as bacteria but COVID-19, for example, is only about one-tenth of a micrometre. The science of microbiology developed with bacteria, along with cellular fungi and protozoa, in one stream, and viruses in another. In common, they all have nucleic acids which have only been characterised since James Watson and Francis Crick discovered the double helix structure of DNA in 1953. Medicine has usually been concerned with the microbes that cause disease, but some have beneficial effects such as those which aid digestion in the gut. Microbes in the environment can be harmful, such as those which cause plant diseases, or beneficial, such as those which improve plant nutrient cycling and those which break down pollutants. Most identification and early studies in the laboratory were with single species in pure culture, although viruses could only be grown with host animal or plant cells. This contrasts the real world where microbes associate with each other in microbial communities.
Infectious Disease
Published in John S. Axford, Chris A. O'Callaghan, Medicine for Finals and Beyond, 2023
Susanna J. Dunachie, Hanif Esmail, Ruth Corrigan, Maria Dudareva
Bacteria are identified or speciated by using a series of physical characteristics (see Figure 3.8). Some of these are listed below. Gram reaction to staining with crystal violet: Gram-positive bacteria stain purple due to their thick layer of peptidoglycan in the cell wall retaining the dye, while Gram-negative bacteria stain red, because their thinner peptidoglycan wall does not retain the crystal violet dye during the decolouring process. Gram-positive and Gram-negative bacteria respond differently to antibiotics.Cell shape: Bacteria can be cocci, bacilli or spirals.Atmospheric preference: Organisms are aerobic, requiring oxygen, or anaerobic, requiring an atmosphere with very little or no oxygen. Organisms that grow in either atmosphere are known as facultative anaerobes.Requirement for special media or intracellular growth.
Bacteria
Published in Julius P. Kreier, Infection, Resistance, and Immunity, 2022
There is a phenomenal variety of shapes and groupings of cells among the prokaryotes. Shapes include the forms historically described as: spherical (cocci), cylindrical (bacilli), either straight or curved (vibrio). The organisms may grow singly or in pairs (diplococci or diplobacilli), in chains (streptococci or streptoba-cilli), in three-dimensional cubes of spheres (sarcinae), or in randomly arranged clusters (staphylococci); in more or less tightly coiled spirals (e.g., spirochaetes), in long sometimes branched filaments (found in Streptomyces and Actinomyces species, among others), in squares, and in irregular clusters. In addition to those already described, groupings of cells include: rosette clusters, flexible gliding clusters, and tightly packed films. It seems reasonable to assume that any possible form, shape or arrangement of bacterial cells may exist somewhere in nature awaiting discovery.
Diagnostic performance of urine analysis based on flow microimaging and artificial intelligence recognition technology in suspected urinary tract infection patients
Published in Scandinavian Journal of Clinical and Laboratory Investigation, 2022
Feng Dong, Yong Yao, Yanyan Chen, Yu Guo, Chao Jing, Jun Wu
MUS-3600 performance was evaluated using suspensions of E. coli ATCC25922 and S. aureus ATCC25923. Good classification of bacilli and cocci and counting ability was shown by comparison with standard urinary culture. Bacillus counts met the regression analysis requirement (a = 0.9849; R2=0.9896; Figure 1). Only bacilli could be detected in samples B1-B7 but cocci were present giving the proportional relation (a = 1.9141) shown in Figure 2. Graphic recognition may identify the two ends of a bacillus as dots during the focusing process and mistakenly identify the dots as cocci when their diameters meet. Samples (C1–C7), containing cocci, displayed a good linear regression (a = 0.9601, R2=0.9965). In similar manner to that seen with the bacilli, when cocci were nondispersed and associated into rods or chains, they may be misidentified as bacilli. However, misidentification remained at a low level (40–100 μl).
Bacteriophages as tools for biofilm biocontrol in different fields
Published in Biofouling, 2021
Camila Mendes Figueiredo, Marilia Silva Malvezzi Karwowski, Romeu Cassiano Pucci da Silva Ramos, Nicoly Subtil de Oliveira, Lorena Caroline Peña, Everdan Carneiro, Renata Ernlund Freitas de Macedo, Edvaldo Antonio Ribeiro Rosa
Many in vitro experiments (Table 1) have shown that bacteriophages can infect bacterial cells contained within biofilms, and that the depolymerases of some phages can facilitate their penetration into the deepest layers of biofilm through degradation of EPS. These bacteria are involved in an assortment of infections and present a wide variety of cell features (e.g. cocci vs bacilli, Gram-positive vs Gram-negative and susceptible vs resistant). According to different authors, bacteriophages can become a strategy for the prevention and eradication of biofilms. In addition, genetic changes in phages can make them even more effective against biofilms, and the use of a mixture of phages can prevent or minimize possible resistance to viruses. However, before phages can be effectively used, standards for the development, production, dosage, and administration of products must be established in order to guarantee the efficacy and safety of the treatment (Parasion et al. 2014).
The distinct effects of aspirin on platelet aggregation induced by infectious bacteria
Published in Platelets, 2020
Nadji Hannachi, Jean-Pierre Baudoin, Arsha Prasanth, Gilbert Habib, Laurence Camoin-Jau
Secondly, we observed aggregates of mixed platelets and infectious bacteria. Bacteria cocci were located on the surface of the aggregates as well as more deeply in the aggregates between platelets. Cocci were found isolated or arranged as clusters such as typical chains. We found out that after the addition of bacteria, platelets in the aggregates were more packed, and this change in density could be accompanied by a loose of cellular integrity of the platelets. The change in platelets density was more pronounced for S. sanguinis (Figure 1g–h) where platelets became poorly distinguishable in compact pack of amorphous clusters and less pronounced for E. faecalis (Figure 1e–f) with no effect on the cellular integrity of the platelets. For S. aureus, the effect was intermediate, and we noticed the presence of filaments (Figure 1c–d).