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BIO 205L/305W - Bergey's Manual

Step 1. Identify your unknown's group number.

The first thing you'll need to do is determine your unknown's group number. To do that, you will need to consult Bergey's Manual of Determinative Bacteriology (9th edition). There are copies of this book available at Cline Library at the Main Desk. Ask for the book there. You may need to provide the call number, which is: QR81.B47.

To find your group number, look through the table of contents of the manual, and use the table that starts on page 17. Most unknowns will be in one of these groups:

  • Gram-Negative, Aerobic/Microaerophilic Rods and Cocci --Group 4
  • Facultatively Anaerobic Gram-Negative Rods --Group 5
  • Gram-Positive Cocci --Group 17
  • Endospore-Forming Gram-Positive Rods and Cocci --Group 18
  • Regular, Nonsporing Gram-Positive Rods --Group 19
  • Irregular, Nonsporing Gram-Positive Rods --Group 20
  • Aerobic, Nonmotile, Nonsporing, Acid-fast, Weakly Gram-Positive Rods --Group 21

Once you think you know your group number (or you have a few possibilities) go to the pages for your group within the manual. From there, you should find more information to help you make a final determination that you have the right group. You might also consult the information below to help you find the best tables to make a final determination about your unknown's group number:

Group #

Table to reference in Bergey’s Determinative, 9th edition

Key differences between genera in this group, as described in the Bio 205L manual


Table 4.1, pp. 103-116

pigments/fluorescent, motility, growth requirements, denitrification, morphology, oxidase


Table 5.1, pg. 202

growth factors, morphology, gram reaction, oxidase


Aerobic genera: Table 17.1, pg 534


Facultatively anaerobic genera: Table 17.2, pg. 535-536


Strictly anaerobic genera: Table 17.3, pg. 537

oxygen requirements, morphology, growth requirements (45°C and supplements)


Table 18.1, pg. 562

oxygen requirements, motility, morphology, catalase


Table 19.1, pg. 568

morphology, oxygen requirements, catalase


Aerobic genera: Table 20.1, pg. 583-584


Facultatively anaerobic genera: Table 20.2, pg. 585-586


Strictly anaerobic genera: Table 20.3, pg. 587-588

catalase, motility, morphology


Table 21.1, pg 598


acid fast, growth

Step 2: Determine the genus of your unknown.

To determine the genus of your unknown, you'll need to keep using Bergey's Manual of Determinative Bacteriology (9th edition). You should have the right group number by now, so go to the pages for your group. These pages should help you identify the genus of your unknown. There might be both tables and descriptions to help you identify the genus. You might find more than one possible match -- that's ok. The next step should provide more information to help you narrow down to a final choice.

Step 3. Read about your genus to make sure you have a match.

Once you have some possibilities for your unknown's genus, follow ALL the instructions below.

1) Open Cline Library’s ebook copy of Bergey's Manual of Systematics of Archaea and Bacteria and then read your next instruction before proceeding. (Note that if you are off campus, once you click the link to Bergey's, you’ll be prompted to log in with your NAU user ID and password.)

2) Next, click the search box in the upper right. Do not click anything else but the search box. (For example, do not click the link to "Log in" and do not click the green button that says "Full Access.")

3. After that, enter your genus name and then click: 



4) If you get a result, read the description to learn more about your genus. Does it seem like you have a match? If so, you are done -- unless you want to proceed to step 4 to try to identify the species of your unknown. If what you read didn't seem like a match, then start this process again. Maybe you missed something. Or, proceed to step 5 for advice on troubleshooting identification problems.

Step 4. (Optional) Identify your unknown to the species level.

The genus description should contain information that helps you differentiate the species in your genus – so, you can compare your lab results to attempt to identify the species of your unknown. Be sure to read both the genus and the species descriptions, because characteristics listed in the genus description aren’t repeated in the species description!

Step 5. Troubleshoot problems.

If you find that the tables in Bergey's Manual of Determinative Bacteriology, 9th edition only allowed you to identify your bacteria down to the family level, then search the Systematic manual (link provided above) for your family name to see if the family description contains the tables you need to narrow down from family to genus. If the Systematic manual DOESN’T contain the tables you need, then you’ll have to come to the Main Desk at Cline Library and to once again consult Bergey's Manual of Determinative Bacteriology, 9th edition. Look up your family name in the index of the Determinative manual to see if there are tables you need that you previously missed.

Also keep in mind that sometimes a taxonomic name can be declared a synonym of another name, and thus is no longer used. Try looking your name up in either of these two resources: 

If you find that another name is being used, look that name up in Bergey's instead. For example, the genus name Aurobacterium has been synonomized with Microbacterium, so you'd look up Microbacterium instead.

Need help?

Your librarian created these instructions, but if you find them confusing, or you run into problems and need help, then don't hesitate to contact your librarian, Mary DeJong, at