Spread and Control of Microbes
Jim Lynch in 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 Diseases
Lyle D. Broemeling in Bayesian Analysis of Infectious Diseases, 2021
Bacteria are about 1,000 times larger than viruses and are more independent. Single-cell organisms that are visible under a microscope are known as “prokaryotic”, and they are quite primitive that they lack a membrane-bound nucleus with linear chromosomes inside. Instead, bacteria usually have a tangled necklace of DNA joined at the extremities, and often smaller rings of DNA referred to as plasmids, which contain genes that allow the bacteria to manufacture proteins beyond its usual repertoire. Unlike more advanced organisms, bacteria carry one set of chromosomes instead of two, an arrangement that implies that every gene is needed, and every selective advantage must be maintained. By taking in new genetic material instead of slowly adapting over millions of years, they evolve sporadically in quantum bursts. Bacteria appear on three forms: spherical (coccus), rodlike (bacillus), and curved (vibrio, spirillum, or spirochete). They are ancient and found as fossils in layers more than three million years ago. Over that time, bacteria have developed a wide range of behaviors over a large variety of environments.
Infectious Disease
John S. Axford, Chris A. O'Callaghan in Medicine for Finals and Beyond, 2023
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.
Isolation and cultivation of candidate phyla radiation Saccharibacteria (TM7) bacteria in coculture with bacterial hosts
Published in Journal of Oral Microbiology, 2020
Pallavi P. Murugkar, Andrew J. Collins, Tsute Chen, Floyd E. Dewhirst
Each of the 32 Saccharibacteria we have isolated has been passed through a 0.2 µm membrane filter. Those visualized by microscopy are cocci <0.2 um in diameter or coccobacilli with diameter of 0.1–0.2 µm. The small size is also evident in Scanning Electron Micrographs (SEM) that our lab generated (Figure 6).While not excluding the possibility that some Saccharibacteria or members of other CPR phyla are larger than the human oral Saccharibacteria isolates, for sake of argument, we hypothesize there are none. This hypothesis can be convincingly falsified by investigators isolating larger CPR bacteria (in coculture or stable consortia), demonstrating that the isolates can be stably passaged in long-term culture and by making these larger bacterial isolates available to other investigators for verification.
Characterization of the EPS from a thermophilic corrosive consortium
Published in Biofouling, 2019
J. Atalah, L. Blamey, I. Gelineo-Albersheim, J. M. Blamey
Consortium biofilm growing on the surface of aluminum alloy AA7075-T6 was morphologically characterized by scanning electron microscopy (Figure 1). A dense formation showing rod-shaped and coccus-like organisms embedded in an amorphous matrix was observed. This was consistent with the 16S rRNA analysis performed in a previous study, which revealed two main bacterial species in this consortium, one corresponding to the genus Anoxybacillus, and the other identified as an uncultured Staphylococcus (unpublished data). The thickness of the layer was determined using fluorescent microscopy (Figure 2). The development of the biofilm on a surface was also monitored using fluorescent microscopy over a span of 14 days (Figure 2). After 24 h there were signs of colonization of the surface. Development of the biofilm continued during the course of the experiment.
Assessment of efficacy of Oseltamivir-Azithromycin combination therapy in prevention of Influenza-A (H1N1)pdm09 infection complications and rapidity of symptoms relief
Published in Expert Review of Respiratory Medicine, 2020
Azfar Athar Ishaqui, Amer Hayat Khan, Syed Azhar Syed Sulaiman, Muhammad Taher Alsultan, Irfanullah Khan, Atta Abbas Naqvi
Combination treatment group was found to be associated with fewer influenza-associated complications as mentioned in Table 2 which represents the univariate analysis of outcome variables. All the variables, which were found to be statistically significant (P-value < 0.05) in univariate analysis, were included in multivariate regression analysis. Both univariate and multivariate analysis revealed that the incidences of secondary bacterial infections associated with Influenza-A (H1N1)pdm09 infection was found to be statistically less significant in Group-AV+AZ patients (23.4% vs 10.4%; P = 0.019). Gram positive cocci such as Streptococcus spp. and Staphylococcus spp. along with Haemophilus influenzae, Chlamydia pneumonia and Mycoplasma pneumoniae were predominant bacterial isolates associated with secondary bacterial infection in Group-AV patients. Other common pathogens include Pseudomonas aeruginosa, Klebsiella pneumoniae, Methicillin-resistant S. aureus (MRSA), Neisseria meningitides, and Escherichia coli. Azithromycin has good antibacterial activity and sensitivity against many of the above mentioned bacterial pathogens due to which the incidences of secondary bacterial pneumonia infection as complication of severe Influenza-A (H1N1)pdm09 infection were significantly less in Group-AV+AZ patients. Univariate analysis of patients diagnosed with secondary bacterial infections is mentioned in Table 3.
Related Knowledge Centers
- Archaea
- Bacteria
- Cell Wall
- Staphylococcus Aureus
- Streptococcus Pneumoniae
- Bacillus
- Neisseria Gonorrhoeae
- Spiral Bacteria
- Gram-Positive Bacteria
- Diplococcus