Quadrant Streak Method
Quadrant Streak Method - Related Videos
09:03
Pure Cultures and Streak Plating: Isolation of Single Bacterial Colonies from a Mixed Sample
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2023
Source: Tilde Andersson1, Rolf Lood1 1 Department of Clinical Sciences Lund, Division of Infection Medicine, Biomedical Center, Lund University, 221 00 Lund, Sweden Seemingly impossible to determine, microbial biodiversity is truly astounding with an estimated one trillion coexisting species (1,2). Although particularly harsh climates, like the acidic environment of the human stomach (3) or the subglacial lakes of Antarctica (4), may be dominated by a specific species, bacteria are typically...
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Olfactory Behaviors Assayed by Computer Tracking Of Drosophila in a Four-quadrant Olfactometer
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Cited by 4 •
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We describe here a behavioral setup and data analysis method for assaying olfactory responses of up to 100 vinegar flies (Drosophila melanogaster). This system may be used with single or multiple olfactory stimuli, and adaptable for optogenetic activation or silencing of neuronal subsets.
01:19
Abdominal Regions and Quadrants
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To promote clear communication, for instance, about the location of a patient's abdominal pain or a suspicious mass, anatomists and clinicians typically use imaginary lines to categorize the abdominopelvic cavity into either four quadrants or nine regions to identify organs in the cavity. The simpler quadrants approach, which is more commonly used in medicine, subdivides the cavity with one horizontal and one vertical line that intersects at the patient's umbilicus (navel). The four quadrants...
18:00
Aseptic Laboratory Techniques: Plating Methods
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When working with media and reagents used to culture microorganisms, aseptic technique must be practiced to ensure contamination is minimized. A variety of plating methods are routinely used to isolate, propagate, or enumerate bacteria and phage, all of which incorporate procedures that maintain the sterility of experimental materials.
07:05
Ultrasound-guided Botulinum Toxin-A Injections: A Method of Treating Sialorrhea
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Cited by 21 •
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Botulinum toxin is injected into the salivary glands for the treatment of sialorrhea. The ultrasound-guided botulinum toxin injection in both the parotid and submandibular glands demonstrates a sustained efficacy and the absence of serious side effects.
FAQs
Sterilizing the loop between quadrants interrupts cell carryover from one section to the next. This preserves the intended dilution sequence, so later streaks receive fewer cells rather than the full original inoculum. Without this reset, cell density may remain high, making separate colonies less likely and complicating isolation.
Each successive quadrant receives cells spread from the preceding section instead of directly from the entire concentrated inoculum. As the loop moves across the plate, fewer microorganisms are deposited in later areas. After incubation, this spatial reduction in density increases the chance that individual cells develop into visibly separated colonies.
A solid agar surface keeps deposited microorganisms localized rather than allowing them to disperse throughout a liquid. Cells that remain sufficiently separated can produce distinct visible colonies during incubation. Because colonies stay positioned on the plate, researchers can examine their appearance and select one for transfer into a pure culture.
The workflow begins by marking four sections on a solid growth-medium plate and applying the inoculum with a sterile loop. The loop is then used to spread cells successively through the marked quadrants, with sterilization between streaks. The plate is finally incubated under suitable conditions so colonies can develop for examination.
This method is useful when a laboratory needs isolated growth from a mixed or concentrated microbial population. It supports routine bacterial cultivation, contamination assessment, and preparation of samples for identification or biochemical testing. Its main value is producing separated colonies that can be evaluated individually rather than treating the starting population as uniform.
After incubation, individual colonies can be examined and transferred to establish pure cultures. Those cultures provide more consistent material for identification, biochemical testing, microscopy, or genetic analysis. Comparing colony-level results also helps researchers assess whether a sample contains different microorganisms or whether contamination may have affected the culture.