Manual Of Systematic Bacteriology

How I Actually Use This Reference When I Need It

I keep a PDF of the Manual Of Systematic Bacteriology pinned in my browser. It is not a book you read cover to cover. It is a lookup tool for taxonomic identification when you have an isolate and need to nail down its genus, species, and the biochemical profile that separates it from everything else in that cluster. Volume 1 covers the spore-formers, Volume 2 is gram-negative rods, and so on. If you are working in a clinical or environmental microbiology lab and your samples routinely include Bacillus, Pseudomonas, or Clostridium species, this manual is where you go after the API strips and MALDI-TOF give you a borderline result. The way most people use it wrong is by trying to run every single test listed. That is a waste of time and reagents. The manual lists full phenotypic profiles for type strains, but in practice you only need the tests that discriminate the closely related species in your particular group. For example, when I was working with Pseudomonas aeruginosa and its close lookalikes in a wastewater facility, I focused entirely on the growth temperature ranges, oxidase strength, and sugar utilization patterns. Everything else was noise. The manual had 40+ tests per organism listed, but only six of them mattered for differentiating P. aeruginosa from P. putida and P. fluorescens in our setup.

Manual Of Systematic Bacteriology

Here is the practical workflow I use when an isolate does not match a known database entry. First, determine the gram reaction and basic morphology. Then run the key biochemical screens: catalase, oxidase, carbon source utilization if you have the plates, and the salt tolerance test. Once you know which section of the manual applies to your organism, flip to that group and find the species table. Read the differential characters column first, not the full description. That column tells you which test results separate each species. Match your isolate against those differentials only. I ran into a problem last year where a Bacillus isolate from a soil sample looked like B. cereus on all the standard tests but gave a weakly positive lecithinase reaction that did not fit the typical profile. The manual entry for B. cereus says strong lecithinase, but B. mycoides is described as having a diffuse colony margin with rhizoid growth and variable lecithinase activity. I rechecked the colony morphology under low magnification and spotted the faint rhizoid edges that I had missed the first time because I was looking at the plate too quickly. The isolate was B. mycoides, not B. cereus. This happens often when you rush past the macroscopic description and jump straight to the biochemical table. The colony appearance is part of the differential key and it is easy to overlook. Another thing beginners miss is that the manual entries are based on type strains, which means the profiles can look clean and consistent. Your clinical or environmental isolates will show more variation. Growth at 37°C might be reported as positive for a species, but some clinical strains grow sluggishly there. The manual notes these variations in the text, but you have to actually read the paragraph, not just the summary table. I learned that the hard way with a Clostridium isolate that tested negative for gelatin hydrolysis when the species key said it should be positive. The full description mentioned that some strains lose gelatinase activity after repeated subculturing, and my isolate had been passaged four times already. One passage in fresh medium and the test came back positive on the second attempt.

The manual is freely available through the International Journal of Systematic and Evolutionary Microbiology website. The ICSU International Committee on Systematics of Prokaryotes maintains it, and the publisher Berghaus offers both print and digital versions. You do not need to buy it. Search for the ICSHP or the journal website and download the relevant volume as a PDF. The search function within the PDF is slow because the files are large, so I keep a separate Excel sheet with the key differential tests for the genera I work with most, linked to the corresponding manual page numbers. That cuts my lookup time from about 20 minutes to roughly three minutes per isolate. There are real limitations to relying on this manual alone. Phenotypic methods have a high rate of misidentification for closely related species. Two Enterobacter species can share nearly identical biochemical profiles and still be genetically distinct. If your lab has access to 16S rRNA sequencing or whole genome sequencing, use it to confirm any identification that the manual gives you. The manual is best used as a first-pass tool to narrow down possibilities, not as the final answer. I have seen labs spend weeks running biochemical panels when a single sequencing run would have settled it in a day. The other limitation is that the manual does not cover newly described species in real time. New bacterial taxa are published in the IJSEM every week, and the next printed volume may not include them for years. If you are working with organisms from unusual environments or newly isolated strains, check the List of Prokaryotic names with Standing in Nomenclature online before you commit to an identification from the manual. It takes about two minutes and saves you from publishing a name that is already invalid or from misidentifying a strain that has been renamed twice in the last five years.

For the actual download, go to the Berghaus digital library or the IJSEM companion site. The volumes are organized by phylum and genus, so you can download just the ones relevant to your work instead of the entire set. The file sizes range from 80 MB to 250 MB per volume. The text is searchable but the tables are sometimes embedded as images in older PDFs, which means you cannot search inside them. Keep that in mind when you need to look up a specific test result across multiple species.