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Published in Firdos Alam Khan, Biotechnology Fundamentals, 2018
A pure culture theoretically contains a single bacterial species. There are a number of procedures available for the isolation of pure cultures from mixed populations. A pure culture may be isolated by the use of special media with specific chemical or physical agents that allow the enrichment or selection of one organism over another. Simpler methods for isolation of a pure culture include (1) spread plating on solid agar medium with a glass spreader and (2) streak plating with a loop. The purpose of spread plating and streak plating is to isolate individual bacterial cells (colony-forming units) on a nutrient medium. Both procedures (spread plating and streak plating) require understanding of the aseptic technique. Asepsis can be defined as the absence of infectious microorganisms, although the term is usually applied to any technique designed to keep unwanted microorganisms from contaminating sterile materials.
Modern Microscopic Methods of Bioaerosol Analysis
Published in Christopher S. Cox, Christopher M. Wathes, Bioaerosols Handbook, 2020
In the origins of microbiology at the end of the last century and the first half of this century, sophisticated procedures were developed for the classification of microorganisms. This was largely as a result of recent discoveries demonstrating that microorganisms are an important cause of human disease. Identification of microorganisms, in particular bacteria, were based principally on the techniques of culturing using solid and streak plate or pour plate methods, from which the organisms were isolated and identified. Early taxonomists relied mainly on cell size, cell shape, the form of colonies, the growth in various types of broth, histological staining and pathogenicity. Hundreds of such identification methods now are described in the literature.4 Examples of a few general texts are given in the references.5–12 Over the last 40 years, it has become accepted generally that the air is an important route for disease transmission. This has led to many advances in the measurement of airborne viable organisms. The majority of sampling techniques still are concerned with counting and identifying bacteria, although methods have been developed specifically for viruses, fungi and yeast as well. More recently, problems such as hay fever and asthma have led to further interest in counting and classifying pollen grains, fungal spores and other biological allergenic materials. It is clearly important to sample airborne biogenic material in places such as hospitals, near sewage works, around or inside industrial plants and military establishments, in clean rooms, and in areas where people or their livestock and crops are concentrated (see also Chapters 18–21).
Methods for Contamination Detection
Published in Jeanne Moldenhauer, Disinfection and Decontamination, 2018
In recent years, this expectation has extended to other types of manufacturing processes. Additionally, many chapters of the USP as well as FD-483 observations and warning letters have stated a need to use environmental isolates when performing method suitability or qualification studies. There are several options for storing microorganisms, e.g., creation of “stock” cultures by microbiological isolate companies, creation of “bioball” cultures, low temperature freezing of cultures, and cryopreservation.
Occurrence of antibiotic resistance among Enterobacterales isolated from raw and ready-to-eat food – phenotypic and genotypic characteristics
Published in International Journal of Environmental Health Research, 2022
Urszula Zarzecka, Wioleta Chajęcka-Wierzchowska, Anna Zadernowska
The isolates were obtained from 80 food samples of 4 groups: raw meat, ready-to-eat food of animal origin, raw plant-derived food, and ready-to-eat salads (n = 20 each). The list of food samples is summarized in Table 1. The food samples were purchased at supermarkets and restaurants in Warmian-Masurian Voivodeship, Poland. The samples were transported to the laboratory in a cold chain at 4 °C and the analysis were started on the same day, within 4 hours of purchase. An amount of 10 g was homogenized in 90 ml buffered peptone water (Merck, Germany) and incubated at 37 °C for 24 h. Then, a loop full culture was streaked on a VRBL (crystal violet, neutral red, bile salts, lactose) agar (Merck, Germany) and incubated in 37 °C for 24 h. Typically, 1 to 5 colonies with morphology typical for Enterobacterales were selected. Presumptive identification of isolates was carried out with the Gram staining and test for catalase and oxidase production. Prior to the analysis, isolates were stored in a Microbank at −80 °C (Biocorp, Poland).
Characterization of low-density polyethylene (LDPE) films degraded using bacteria strains isolated from oil-contaminated soil
Published in Environmental Technology, 2023
Godswill E. Akhigbe, Adebisi E. EnochOghene, Kayode O. Olumurewa, Oluwasegun B. Koleoso, Ngozi D. Ogbonna
Soil samples were collected in sterile sample bags at the depth of 5–15 cm from a transformer oil spillage site in Ile-Ife, Osun State, Nigeria, and taken immediately to the laboratory for microbial analysis. A stock solution was prepared by introducing 1 g of the soil sample in 10 mL distilled water, thereafter, serial dilutions were carried out by introducing 1 mL of the stock in 9 mL distilled water to make a concentration of 10−1. This was further diluted till a concentration of 10–6 was reached. A concentration of 0.1 mL of 10–4 concentration was plated on nutrient agar and incubated at 37°C for 18–24 hrs. Colonies obtained were sub-cultured to obtain pure isolates which were used for downstream analysis.
Characterization of the emulsifying activity of biosurfactants produced by lactic acid bacteria isolated from the Argentinian Patagonia
Published in Journal of Dispersion Science and Technology, 2022
Virginia M. Lara, Marisol Vallejo, Romina Parada, Johan S. Henao Ossa, María F. Gliemmo, Carmen A. Campos
Samples from cheese were carried to the laboratory at 4 °C and then they were kept frozen at −30 °C until processed. An aliquot (1 g) was homogenized in 9 mL sterile 0.9% (w/v) NaCl, 10-fold diluted and plated on Man Rogosa Sharp (MRS) agar (Biokar Diagnostics, Beauvais, France) supplemented 20 µg/mL nalidixic acid (Sigma Aldrich, St. Louis, MO, USA) and 10 µg/mL cycloheximide (Sigma Aldrich, St. Louis, MO, USA). After incubation at 37 °C for 48 h, individual colonies were picked off to a new isolated plate. Isolates were maintained as frozen stocks at −30 °C.