A fastidious organism is any organism that has complex or particular nutritional requirements. In other words, a fastidious organism will only grow when specific nutrients are included in its medium. The more restrictive term fastidious microorganism is used in microbiology to describe microorganisms that will grow only if special nutrients are present in their culture medium. [1] Thus fastidiousness is often practically defined as being difficult to culture, by any method yet tried.
An example of a fastidious bacterium is Neisseria gonorrhoeae , which requires blood or hemoglobin and several amino acids and vitamins to grow. [2] Other examples include Campylobacter spp. and Helicobacter spp., which are capnophilic – require elevated CO2 – among other requirements. Fastidious organisms are not inherently "weak"—they can flourish and thrive in their particular ecological niche with its particular nutrients, temperature, and absence of competitors, and they can be quite difficult to kill off. But they are difficult to culture simply because it is difficult to accurately simulate their natural milieu in a culture medium. For example, Treponema pallidum is not easy to culture, yet it is resilient in its preferred environment, being difficult to eradicate from all tissues of a person with syphilis.
An example of the practical relevance of fastidiousness is that a negative culture result could be a false negative; that is, just because culturing failed to produce the organism of interest does not mean that the organism was absent from either the sample, the place where the sample came from, or both. This means that the sensitivity of the test is less than perfect. So, for example, culture alone may not be enough to help a doctor trying to find out which bacteria is causing pneumonia or sepsis in a hospitalized patient, and therefore which antibiotic to use. When there is a need to determine which bacteria or fungi are present (in agriculture, medicine, or biotechnology), scientists can also turn to other tools besides cultures, such as nucleic acid tests (which instead detect that organism's DNA or RNA, even if only in fragments or spores as opposed to entire cells) or immunologic tests (which instead detect its antigens, even if only in fragments or spores as opposed to entire cells). The latter tests may be helpful in addition to (or instead of) culture, although circumspection is required in interpreting their results, too, because the DNA, RNA, and antigens of many different bacteria and fungi are often much more prevalent (in air, soil, water, and human bodies) than is popularly imagined—at least in tiny amounts. So a positive on those tests can sometimes be a false positive regarding the important distinction of infection versus just colonization or ungerminated spores. (The same problem also causes confounding errors in DNA testing in forensics; tiny amounts of one's DNA can end up almost anywhere, such as in transfer by fomites, and because modern tests can recover such tiny amounts, the interpretation of their presence requires due circumspection. [3] ) Such considerations are why skill is needed in deciding which test is appropriate to use in a given situation and in interpreting the results.
Some microbial species' requirements for life include not only particular nutrients but chemical signals of various kinds, some of which depend, both directly and indirectly, on other species being nearby. Thus not only nutrient requirements but other chemical requirements can stand in the way of culturing species in isolation.
Lewis Thomas put fastidiousness and the challenge of culturing isolates into logical context in his 1974 book Lives of a Cell : "It has been estimated that we probably have real knowledge of only a small proportion of the microbes of the earth, because most of them cannot be cultivated alone. They live together in dense, interdependent communities, feeding and supporting the environment for each other, regulating the balance of populations between different species by a complex system of chemical signals. With our present technology, we can no more isolate one from the rest, and rear it alone, than we can keep a single bee from drying up like a desquamated cell when removed from his hive." [4] One of the logical corollaries of this passage is that the inseparability of many species from their native ecological contexts is quite natural and reflects only the ubiquity of interdependencies in ecological systems—not any weakness, frailty, stubbornness, or rarity of any species.
Regarding Lewis's point about the limits of humans' ability to discover greater knowledge of microbes—from individual species and strains to whole microbial communities—another pair of facts is relevant. On one hand, it is true that in the decades since he wrote Lives of a Cell, the development of omics, made possible by greatly increased throughput of sequencing and digital analytics of the resultant data, has greatly expanded humans' ability to learn more about microbes because their aggregated biochemical footprints and fingerprints, as it were, can now be analyzed and quantified (for example, genomics, microbiomics, metabolomics, metagenomics/ecogenomics). But on the other hand, for learning more about prokaryotes, the limits of culturing are still relevant even after the -omics revolution, for about the same reason that in eukaryote pathology, cytopathology still needs histopathology as its whole-tissue counterpart: there are things we can learn from whole microbial cells that we can't learn from their constituent molecules alone, just as there are things we can learn from whole eukaryotic tissues that we can't learn from their constituent cells alone (for example, the limits of aspiration cytology alone versus histopathology in concert).
A microorganism, or microbe, is an organism of microscopic size, which may exist in its single-celled form or as a colony of cells.
Bacterial growth is proliferation of bacterium into two daughter cells, in a process called binary fission. Providing no event occurs, the resulting daughter cells are genetically identical to the original cell. Hence, bacterial growth occurs. Both daughter cells from the division do not necessarily survive. However, if the surviving number exceeds unity on average, the bacterial population undergoes exponential growth. The measurement of an exponential bacterial growth curve in batch culture was traditionally a part of the training of all microbiologists; the basic means requires bacterial enumeration by direct and individual, direct and bulk (biomass), indirect and individual, or indirect and bulk methods. Models reconcile theory with the measurements.
An endospore is a dormant, tough, and non-reproductive structure produced by some bacteria in the phylum Bacillota. The name "endospore" is suggestive of a spore or seed-like form, but it is not a true spore. It is a stripped-down, dormant form to which the bacterium can reduce itself. Endospore formation is usually triggered by a lack of nutrients, and usually occurs in gram-positive bacteria. In endospore formation, the bacterium divides within its cell wall, and one side then engulfs the other. Endospores enable bacteria to lie dormant for extended periods, even centuries. There are many reports of spores remaining viable over 10,000 years, and revival of spores millions of years old has been claimed. There is one report of viable spores of Bacillus marismortui in salt crystals approximately 250 million years old. When the environment becomes more favorable, the endospore can reactivate itself into a vegetative state. Most types of bacteria cannot change to the endospore form. Examples of bacterial species that can form endospores include Bacillus cereus, Bacillus anthracis, Bacillus thuringiensis, Clostridium botulinum, and Clostridium tetani.
Neisseria gonorrhoeae, also known as gonococcus (singular), or gonococci (plural), is a species of Gram-negative diplococci bacteria isolated by Albert Neisser in 1879. It causes the sexually transmitted genitourinary infection gonorrhea as well as other forms of gonococcal disease including disseminated gonococcemia, septic arthritis, and gonococcal ophthalmia neonatorum.
Neisseria is a large genus of bacteria that colonize the mucosal surfaces of many animals. Of the 11 species that colonize humans, only two are pathogens, N. meningitidis and N. gonorrhoeae.
An agar plate is a Petri dish that contains a growth medium solidified with agar, used to culture microorganisms. Sometimes selective compounds are added to influence growth, such as antibiotics.
A microbiological culture, or microbial culture, is a method of multiplying microbial organisms by letting them reproduce in predetermined culture medium under controlled laboratory conditions. Microbial cultures are foundational and basic diagnostic methods used as a research tool in molecular biology.
Microbial ecology is the ecology of microorganisms: their relationship with one another and with their environment. It concerns the three major domains of life—Eukaryota, Archaea, and Bacteria—as well as viruses.
A growth medium or culture medium is a solid, liquid, or semi-solid designed to support the growth of a population of microorganisms or cells via the process of cell proliferation or small plants like the moss Physcomitrella patens. Different types of media are used for growing different types of cells.
Neisseria meningitidis, often referred to as meningococcus, is a Gram-negative bacterium that can cause meningitis and other forms of meningococcal disease such as meningococcemia, a life-threatening sepsis. The bacterium is referred to as a coccus because it is round, and more specifically a diplococcus because of its tendency to form pairs.
Microbial genetics is a subject area within microbiology and genetic engineering. Microbial genetics studies microorganisms for different purposes. The microorganisms that are observed are bacteria, and archaea. Some fungi and protozoa are also subjects used to study in this field. The studies of microorganisms involve studies of genotype and expression system. Genotypes are the inherited compositions of an organism. Genetic Engineering is a field of work and study within microbial genetics. The usage of recombinant DNA technology is a process of this work. The process involves creating recombinant DNA molecules through manipulating a DNA sequence. That DNA created is then in contact with a host organism. Cloning is also an example of genetic engineering.
Food microbiology is the study of the microorganisms that inhabit, create, or contaminate food. This includes the study of microorganisms causing food spoilage; pathogens that may cause disease ; microbes used to produce fermented foods such as cheese, yogurt, bread, beer, and wine; and microbes with other useful roles, such as producing probiotics.
Bacteria are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep biosphere of Earth's crust. Bacteria are vital in many stages of the nutrient cycle by recycling nutrients such as the fixation of nitrogen from the atmosphere. The nutrient cycle includes the decomposition of dead bodies; bacteria are responsible for the putrefaction stage in this process. In the biological communities surrounding hydrothermal vents and cold seeps, extremophile bacteria provide the nutrients needed to sustain life by converting dissolved compounds, such as hydrogen sulphide and methane, to energy. Bacteria also live in symbiotic and parasitic relationships with plants and animals. Most bacteria have not been characterised and there are many species that cannot be grown in the laboratory. The study of bacteria is known as bacteriology, a branch of microbiology.
Medical microbiology, the large subset of microbiology that is applied to medicine, is a branch of medical science concerned with the prevention, diagnosis and treatment of infectious diseases. In addition, this field of science studies various clinical applications of microbes for the improvement of health. There are four kinds of microorganisms that cause infectious disease: bacteria, fungi, parasites and viruses, and one type of infectious protein called prion.
Vampirococcus is an informally described genus of ovoid Gram-negative bacteria, but the exact phylogeny remains to be determined. This predatory prokaryote was first described in 1983 by Esteve et al. as small, anaerobic microbe about 0.6 μm wide before being given the name of Vampirococcus in 1986 by Guerrero et al. This prokaryote is a freshwater obligate predator that preys specifically on various species of the photosynthetic purple sulfur bacterium, Chromatium. As an epibiont, Vampirococcus attaches to the cell surface of their prey and "sucks" out the cytoplasm using a specialized cytoplasmic bridge. They are commonly mentioned as an example of epibionts when discussing strategies employed by bacterial predators. This microbe still has yet to be classified based on genomic sequencing or 16S rRNA because it cannot be sustained long enough outside its natural environment to isolate a pure culture.
Marine microorganisms are defined by their habitat as microorganisms living in a marine environment, that is, in the saltwater of a sea or ocean or the brackish water of a coastal estuary. A microorganism is any microscopic living organism or virus, that is too small to see with the unaided human eye without magnification. Microorganisms are very diverse. They can be single-celled or multicellular and include bacteria, archaea, viruses and most protozoa, as well as some fungi, algae, and animals, such as rotifers and copepods. Many macroscopic animals and plants have microscopic juvenile stages. Some microbiologists also classify biologically active entities such as viruses and viroids as microorganisms, but others consider these as non-living.
Soil microbiology is the study of microorganisms in soil, their functions, and how they affect soil properties. It is believed that between two and four billion years ago, the first ancient bacteria and microorganisms came about on Earth's oceans. These bacteria could fix nitrogen, in time multiplied, and as a result released oxygen into the atmosphere. This led to more advanced microorganisms, which are important because they affect soil structure and fertility. Soil microorganisms can be classified as bacteria, actinomycetes, fungi, algae and protozoa. Each of these groups has characteristics that define them and their functions in soil.
The NYC medium or GC medium agar is used for isolating Gonococci.
In microbiology, the term isolation refers to the separation of a strain from a natural, mixed population of living microbes, as present in the environment, for example in water or soil, or from living beings with skin flora, oral flora or gut flora, in order to identify the microbe(s) of interest. Historically, the laboratory techniques of isolation first developed in the field of bacteriology and parasitology, before those in virology during the 20th century.
Diagnostic microbiology is the study of microbial identification. Since the discovery of the germ theory of disease, scientists have been finding ways to harvest specific organisms. Using methods such as differential media or genome sequencing, physicians and scientists can observe novel functions in organisms for more effective and accurate diagnosis of organisms. Methods used in diagnostic microbiology are often used to take advantage of a particular difference in organisms and attain information about what species it can be identified as, which is often through a reference of previous studies. New studies provide information that others can reference so that scientists can attain a basic understanding of the organism they are examining.