Differential Tests and Bacterial Identification

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Questions and Answers

Which biochemical test is positive for Indole production?

Simmons Citrate

1% Tryptone broth (correct)

Starch agar

Nitrate broth

What does a negative result in a Gram stain indicate?

Presence of Gram-negative bacteria (correct)

Possibility of non-reactive species

Uncertain bacterial classification

Presence of Gram-positive bacteria

Which of the following tests is used to determine motility?

Gelatin media

Blood agar

Nutrient agar (correct)

Fluid thioglycollate media

Which test is used to assess sugar fermentation in Lactose?

Phenol red Lactose Signup and view all the answers

What is important to check before using Bergey’s Manual?

The type of edition to use Signup and view all the answers

Which of the following tests shows a positive result for Nitrate reduction?

Nitrate broth Signup and view all the answers

What kind of bacteria produces the positive results for hydrolysis in the medium tested?

Sugars in Phenol red glucose Signup and view all the answers

How should one begin organizing tests in a flow chart according to the manual?

By noting shapes and motility Signup and view all the answers

What is the primary reason for not tightening the caps on inoculated test tubes?

To allow gas exchange during incubation Signup and view all the answers

What type of media provides essential nutrients like vitamins, minerals, and energy for bacterial growth?

Complex media Signup and view all the answers

Which bacterial identification method involves isolating colonies using a streaking technique?

Quadrant streak Signup and view all the answers

For the identification of an unknown bacterium, what is the first step in the process?

Isolating the causative agent Signup and view all the answers

Which temperature is best suited for incubating bacteria like Escherichia coli?

37˚C Signup and view all the answers

What is the significance of using selective media in bacterial culture?

It inhibits the growth of unwanted species Signup and view all the answers

What is the purpose of performing biochemical tests on bacterial cultures?

To determine metabolic capabilities and identify the organism Signup and view all the answers

In the context of identification, what is Bergey's Manual primarily used for?

Identifying and classifying bacterial species Signup and view all the answers

Which enzyme is used in biochemical tests to assess the breakdown of hydrogen peroxide?

Catalase Signup and view all the answers

Which of the following is NOT a sugar commonly tested for fermentation in biochemical assays?

Fructose Signup and view all the answers

Which type of stain is primarily used to differentiate between gram-positive and gram-negative bacteria?

Gram Stain Signup and view all the answers

Bergey's Manual primarily assists researchers in classifying which type of organisms?

Microorganisms Signup and view all the answers

What type of biochemical reaction does the methyl red test evaluate?

Mixed acid fermentation Signup and view all the answers

Which characteristic distinguishes whether an organism can utilize citrate as a carbon source?

Citrate test Signup and view all the answers

Which of the following enzymes is responsible for the breakdown of fats?

Lipase Signup and view all the answers

In the context of biochemical reactions, what does a positive result typically indicate?

Presence of enzymes or metabolic activity Signup and view all the answers

Study Notes

Differential Tests 1

Today's Inoculation: Work as a table, label all tubes, plates, and the rack, and don't tighten caps on inoculated tubes.
Labeling Your Tubes: Use white masking tape to label each tube with the relevant information: table symbol, section time, test abbreviation, species name, and rack label (e.g., MW11:50 MRVP E.coli)

Biochemistry I

Today's Inoculation: Work as a table, label all tubes, plates, and the rack. Place all inoculated material in the 37°C incubator for 16 hours.

Identification of Unknown Bacterium

Infection?: Mixed culture (Yes/No), first step (what to do next).

Unknown Pathogenic Bacteria

Growth Considerations: Consider nutrients (vitamins, minerals, energy, carbon), selective, differential, complex or defined media, incubation temperature (room, 37°C, 25°C, body temp), and oxygen conditions (aerobic, anaerobic, microaerophilic, or others like pH, salt).
Isolation of Pure Cultures: Grow each colony separately for study.

Identification of Physical Characteristics by Staining

Microorganisms are identified by observable physical characteristics.
Examples of staining methods include simple stains (to identify shape), Gram stain (to distinguish Gram-positive vs. Gram-negative), capsule stain, acid-fast stains (bacteria with mycolic acid in their cell wall), and endospore stains (to observe spore formers)

Identification Through Biochemical Characteristics

Biochemical Characteristics: Organisms are identified based on their ability to produce certain enzymes and metabolize specific molecules.
Degradation enzymes (catalase, urease, nitrate reductase, tryptophanase, lipase) and fermentation of sugars (mannitol, lactose, glucose). Organisms can utilize citrate and malonate, also identifying the type of fermentation end products, including methyl red (MR) and Vogus Proskauer (VP).
Biochemical Results: Biochemical tests results (positive/negative) are used to identify microorganisms.
Importance of Tests: The importance of particular tests used depends on the organization of the resources. For instance, in a healthcare setting, miniaturized test systems are employed to perform many tests simultaneously to accelerate identification.

How to Use Bergey's Manual

Use the Determinative edition, not the Systematic edition.
Complete data tables before accessing the manual. This manual is on reserve at the information commons.
Follow the flow chart of tests from the manual and perform tests to organize and identify organisms based on minimum 7 tests.
Build the flow chart while using the manual. Use PowerPoint (or equivalent) to easily create and position the lines and elements on the chart.

Bergey's Homework Assignment

Submit a completed Unknown data table, a one-page unknown flow chart, a completed Orphan data table, and a single-page orphan flow chart.
The flow charts should identify the unknowns/orphans based on at least seven tests. Multiple-page charts will have points deducted. Use PowerPoint for flow charts.

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Description

This quiz covers differential tests and methods for identifying unknown pathogenic bacteria in Biochemistry I. Focus on techniques for labeling inoculated materials, growth considerations, and isolation processes. Test your understanding and skills on these essential microbiological practices.