Biological Sciences
Culturing Microorganisms
Culturing microorganisms involves the process of growing and maintaining microorganisms in a controlled environment, such as a laboratory setting. This is done to study their characteristics, behavior, and potential applications. Culturing microorganisms typically involves providing them with the necessary nutrients, temperature, and other conditions to support their growth and reproduction.
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8 Key excerpts on "Culturing Microorganisms"
eBook - PDF- Stuart Hogg(Author)
- 2013(Publication Date)
- Wiley-Blackwell(Publisher)
4.3 LABORATORY CULTIVATION OF MICROORGANISMS 89 4.3 Laboratory cultivation of microorganisms Critical to the development of microbiology during its ‘golden age’ were the advances in culturing techniques, which enabled the isolation and pure cul- ture of specific microorganisms. The study of pure cultures made it possible to determine the properties of a specific organism such as its metabolic char- acteristics or its ability to cause a particular disease. It also opened up the possibility of classifying microorganisms, on the basis of the characteristics they display in pure culture. The artificial culture of any organism requires a supply of the necessary nutrients, together with the provision of appropriate conditions such as tem- perature, pH and oxygen concentration. The nutrients and conditions pro- vided in the laboratory are usually a reflection of those found in the organ- ism’s natural habitat. It is also essential that appropriate steps are taken to avoid contamination (Box 4.1). In the next section we shall describe the tech- niques used to isolate and propagate microorganisms in the laboratory. 4.3.1 Obtaining a pure culture Microorganisms in the natural world do not live in pure cultures, but exist as part of complex ecosystems comprising numerous other organisms. The first step in the cultivation of specific microorganisms is therefore the creation of a pure culture. A key development for the production of pure cultures was the ability to grow microorganisms on a solid medium. Koch had noticed Box 4.1 Aseptic technique Most commonly used culture media will support the growth of a number of different bacteria. It is therefore essential when working in the microbi- ology laboratory that suitable precautions are taken to prevent the growth of unwanted contaminants in our cultures. These simple practical measures are termed aseptic technique, and it is essential to master them if reliable experimental results are to be obtained.
- David M. Carlberg(Author)
- 2004(Publication Date)
- CRC Press(Publisher)
In the case of viruses and other more fastidious microorganisms, living cells or whole plants or animals must be used as hosts. In either case, care must be taken to supply all the chemical and physical conditions (temperature, atmosphere, etc.) necessary to support the desired organisms and, when appropriate, their hosts, as well. There are many techniques at the disposal of the microbiologist for measuring microbial populations; some determine only culturable popula-tions, others measure total (culturable, viable but nonculturable, and non-viable) cell numbers. There is no one ideal method, and frequently one must rely on two or more different techniques to satisfy a particular need. Due to the large populations normally involved, cultivating microor-ganisms may expose laboratory and maintenance personnel and the general public to certain hazards. Special precautions should be practiced whenever microbial cultures are handled and discarded.
eBook - ePub- Rodney P. Anderson, Linda Young(Authors)
- 2016(Publication Date)
- Wiley(Publisher)
T he ability to isolate and grow a microorganism in the laboratory makes the identification for medical purposes possible and the study of its structure and physiology easier. It also allows for in vitro testing of potential antimicrobial agents against pathogenic organisms. Although most microbes cannot currently be grown in the laboratory, we have learned a significant amount about the basics of how to cultivate microbes in laboratory media.Microbes are grown in a laboratory setting in a growth medium, an artificial liquid or gel containing nutrients designed to meet the microbes’ specific growth requirements. Growth in the medium is initiated by placing an inoculum, a small sample of microorganisms, into the growth medium to produce a culture. The growth medium that receives the inoculum needs to be sterile initially so the culture grows only the desired microbes. Microbial samples for growth can come from a patient specimen or from environmental samples.Obtaining a Pure Culture
Microbes naturally grow in complex communities. To identify and study a single type of microbe, such as a bacterial pathogen, it is necessary to first isolate it from the other microbes with which it grows. As an isolated bacterial cell divides, it grows into a colony, a visible mass of cells descended from a single cell. Because the colony is derived from a single ancestor, it is a pure culture.A pure culture from a sample containing a mixed population of microbes can be obtained by the streak plate method (Figure 9.9
- Carlos Ricardo Soccol, Ashok Pandey, Christian Larroche(Authors)
- 2013(Publication Date)
- CRC Press(Publisher)
At present, it is related to the processes of standardization and preparation of products of high quality, but it also involves foresight into the future development of the biotechnology (Boeswinkel 1976; Vinci and Byng 1999). 2.2 ISOLATION OF MICROORGANISMS The first stage in the screening for microorganisms of potential industrial application is their isolation. Isolation involves obtaining either pure or mixed cultures followed by their assessment to determine the desired reaction or process for the desired prod-uct. The isolate must eventually carry out the process economically. Therefore, the selection of the culture to be used is a compromise between the productivity of the organism and the economic constraints of the process criteria as being important in the choice of organism (Anon. 1979, 1984): • The nutritional characteristics of the organism: using a very cheap medium or a predetermined one • The optimum temperature of the organism • The reaction of the organism with the equipment to be employed and the suitability of the organism to the type of process to be used • The stability of the organism and its amenability to genetic manipulation • The productivity of the organism, measured in its ability to convert sub-strate into product and to give a high yield of product per unit time • The ease of product recovery from the culture 2.2.1 I SOLATION M ETHODS Microorganisms are thought ubiquitous in their occurrence; common sources for their isolation are soils, lakes, and river muds. The technique of isolating micro-organisms also varies according to the nature and physiological properties of the microbe to be isolated. For example, isolation of fungi from a mixture of fungi and bacteria can be achieved easily by incorporating antibiotics to which the bacteria are sensitive in the growth medium. Similarly, from a mixture of sporulating (spore forming) and nonsporulating bacteria, spore-forming bacteria can be isolated by
eBook - PDF- Dave Wessner, Christine Dupont, Trevor Charles, Josh Neufeld(Authors)
- 2020(Publication Date)
- Wiley(Publisher)
For organisms in a batch culture, life is boom and bust— rapid exponential growth when resources are abundant followed by stasis and perhaps death when resources are exhausted. This pattern is common in dynamic habitats. For example, when an animal or a plant dies, microorganisms take advantage of the abundant nutrients in the dead mate- rial and proliferate madly as they consume it. The micro- bial population expands dramatically as the dead material Air supply Sampling port Fresh medium Pump Control valve Culture vessel Collection vessel FIGURE 7.17 A continuous culture system Chemostats provide a means of maintaining exponentially growing cells under constant conditions for the study of microbial physiology. The most basic form consists of a culture vessel with an inlet port for addition of sterile medium and an outlet port for draining culture from the vessel at the same rate as fresh media is added to keep the culture at a constant volume. The apparatus shown here also has a port for sterile addition of air, a necessity when growing organisms requiring aerobic metabolism. 7.4 Eliminating Microbes and Preventing their Growth 257 7.3 Fact Check 1. How can we count viable cells? 2. What are the advantages of measuring turbidity? 3. Describe the parts of a typical bacterial growth curve. 4. How can we determine the growth rate of a microorganism? 5. What is a continuous culture? 7.4 Eliminating Microbes and Preventing their Growth • How can we eliminate microbes or inhibit their growth? So far in this chapter, we’ve focused primarily on the growth of microorganisms. In many situations, though, we may want to prevent the growth of microbes, kill them, or physically remove them. In the laboratory, we want to be certain that unwanted bacteria do not contaminate glassware and reagents.
- Khuntia, B K(Authors)
- 2021(Publication Date)
- Daya Publishing House(Publisher)
6 Cultivation of Bacteria Bacteria are present universally almost everywhere; in soil, air, water and even inside mouth and intestine of all animals. ‘Cultivation of bacteria’ or ‘bacteria culture’ means growing these minute invisible bacteria in nutritionally rich substances and suitable environmental conditions, which support their rapid growth and multiplication. This results in their manifestation as large population visible to naked eye (as colonies or turbid suspension). Thus, there are two basic requirements for the cultivation of bacteria, such as ( I ) Abundant nutrients and ( II ) Optimum environmental conditions. ( I ) Abundant Nutrients In nature, bacteria take up the complex nutrients available around them after degrading them into simpler forms by the enzymes secreted by them. But in laboratory, rapid growth is augmented by growing them in substances containing nutrients in simpler forms. These substances containing adequate quantity of nutrients in simpler forms for rapid growth and multiplication of bacteria are called ‘culture media’. There are a number of culture media now available containing different ingredients ( See page 59-61 and Appendix I ). Culture media are obtained in the following three ‘physical forms’. 1. Liquid Media or Broth These are clear liquids containing water and nutrients in simpler forms for growth of bacteria, which have been sterilised in autoclave. When bacteria is inoculated into them and incubated in conditions suitable for their growth, they grow profusely into thick suspensions of bacteria cells, due to which the media become turbid. 2. Solid Media This ebook is exclusively for this university only. Cannot be resold/distributed. These are solidified substances, in which liquid broths have been supplemented with a solidifying agent called ‘agar’, at a level more than 1%. Agar is a powder (sometimes called agar agar) extracted from seaweeds and is a complex carbohydrate composed mainly of galactose.
eBook - PDF- H W Doelle(Author)
- 1994(Publication Date)
- WSPC(Publisher)
CHAPTER 4 Maintenance and Preservation of MicrobiaX Cultures L.I.SLY 1. Introduction The efficient practice of microbiology relies on the use of cultures of microorganisms. Authentic reference strains are required for comparison with laboratory iso-lates, for control cultures in standard methods of analysis, and for use in research and teaching. Biotechnologists also require cultures for use in various industrial processes. There is amongst microorganisms an inherent tendency to mutate in laboratory culture. It is essential that labora-tories use procedures to maintain their cultures in a viable and genetically stable state. Various methods have been established to preserve cultures so that the minimum genetic d r i f t occurs. This chapter summarises some of the preservation methods available, and discusses the procedures used to organize the various operations that must be co-ordinated for the efficient management of a culture collec-tion. 2. Stock culture maintenance Easy access to actively growing cultures is a require-ment of most microbiological laboratories. Cultures are routinely required generally on a day to day basis for quality control, comparative testing, inocula for bioassays and for various other reasons. New isolates or accessions are usually maintained as actively growing stocks until the strain can be confidently preserved by one or more of the long-term methods available. There are some cultures for which no long-term preservation methods are available and these cultures must be continually maintained in active culture. Periodic transfer or subculture is the traditional method used by microbiologists to maintain isolates in the laboratory. However, to minimize genetic change and for reasons of financial and labour savings i t is advisable to engage in as l i t t l e subculturing as possible and to have back-up stocks of well preserved cultures. Periodic sub-culture is not recommended for long term preservation.
eBook - PDF- Rodney P. Anderson, Linda Young, Kim R. Finer(Authors)
- 2020(Publication Date)
- Wiley(Publisher)
How- ever, typically, as the bacterial cells multiply, conditions become increasingly less favorable, and the growth rate slows. When microbiologists refer to microbial growth, they are normally referring to an increase in the number of individuals in a population, not to an increase in the size of the individual microbes. Microbial growth requires raw materials, energy, and genetic blueprints to produce new microbes and increase pop- ulation size. This chapter analyzes the requirements for micro- bial growth, how we use that knowledge to grow microbes in the lab for identification, and the physical and chemical meth- ods we use to control it. 257 258 CHAPTER 11 Microbial Growth and Control TABLE 11.1 Classification of Living Microorganisms by Energy and Carbon Source Energy Source Carbon Source Classification Example Light Organic molecules Photoheterotroph Rhodobacter Inorganic molecules Photoautotroph Anabaena Chemicals Organic molecules Chemoheterotroph Staphylococcus Inorganic molecules Chemoautotroph Acidithiobacillus ferrooxicans 11.1 Requirements for Microbial Growth LEARNING OBJECTIVES 1. Describe the energy sources used by microbes. 2. Explain the physical requirements for microbial growth, including pH, temperature, and osmolarity. 3. Describe the chemical requirements for microbial growth. Microbes require a constant supply of energy to make ade- nosine triphosphate (ATP), which, in turn, is the source of energy for the metabolic processes necessary to produce new cells (see Remember This!). A microbe must also have a habitat for reproduction that is within the range of the physical and chemical parameters that allow for metabolic function. In a laboratory, this habitat is provided through a culture. Physical requirements include appropriate acidity (pH), temperature, and osmolarity, whereas chemical requirements involve levels of oxygen and other essential elements.
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