Scientific names of bacteria in academic writing: Style tips + Checklist

Scientific names are labels for precise identification; they are ‘keys’ that can unlock vaults of information. Compare the kind of information that can be retrieved by typing the scientific name of an organism – instead of its common name – in the search box of a search engine, and you will realize that the analogy of a key is particularly appropriate.

An earlier article discussed some points of style related to scientific names of organisms in general whereas this article focuses on bacteria. Bacterial names are governed by the International Code of Nomenclature of Bacteria.

The Basics of Bacterial Binomial Names

Bacterial species are identified using a two-part naming system called binomial nomenclature, governed by the International Code of Nomenclature of Prokaryotes (ICNP).

How a Bacterial Species Name Is Structured

Every bacterial name has two components:

• Genus name: always capitalized (e.g., Staphylococcus)
• Specific epithet: always lowercase (e.g., aureus)

Together, they form the species name: Staphylococcus aureus. Both parts must always be italicized (or underlined in handwritten or typed text). The genus name is never written alone as a stand-in for the species.

When to Write the Full Name vs. an Abbreviation

• Write the full name at first mention in the main text: Escherichia coli
• After the first mention, abbreviate the genus to its initial letter: E. coli
• If multiple genera share the same initial letter in your paper, do not abbreviate — spell out both names in full to avoid confusion
• The ICSP recommends spelling out the full name again in the abstract or summary, even if already abbreviated in the body text

How to Handle Unnamed Species (sp. and spp.)

When the species has not been identified or named, use these abbreviations after the genus:

• Moraxella sp.  refers to one unnamed or unidentified species
• Moraxella spp.  refers to more than one unnamed species

Note that sp. and spp. are not italicized, but the genus name preceding them remains in italics.

Bacterial Name Formatting at a Glance

Subspecific Taxa: Below the Species Level

When a species is divided further, additional naming rules apply. These subdivisions sit below species level and each follows its own formatting convention.

Subspecies (subsp.)

• The abbreviation subsp. indicates a subspecies rank
• subsp. is never italicized, but the subspecies epithet that follows it is
• Example: Staphylococcus aureus subsp. aureus
• When the subspecies epithet repeats the species epithet (as above), it designates the nominate subspecies (the one that first established the species name)

Infrasubspecific Subdivisions

Several ranks exist below subspecies level. These are written in plain roman text, with only the following epithet italicized:

• Pathovar (pv.): groups strains by the host plant they infect; e.g., Pseudomonas syringae pv. tomato
• Biovar (bv.): groups strains by biochemical or physiological differences; e.g., Rhizobium leguminosarum bv. viciae
• Serovar: groups strains by their antigenic properties; e.g., Salmonella enterica serovar Typhimurium
• Morphovar: groups strains by morphological differences

Note: the suffix -var has replaced the older -type across all these ranks.

Strain Designations

• Strain designations sit after the species or subspecies name
• They are written in plain roman text and never italicized
• They are typically a combination of letters and numbers
• Example: Escherichia coli O157:H7
• The ICSP does not regulate strain designations; follow your journal’s preferred format

Infrasubspecific Rank Formatting

Style Differences Between Bacterial, Plant, and Animal Names

Bacterial, plant, and animal names are each governed by a different international code. While the core formatting rules (italicization, binomial structure) are shared, several style points differ and are a common source of errors in manuscripts that reference organisms across groups.

Key Style Differences Across Nomenclature Codes

Key Takeaway

Bacterial nomenclature style sits closer to plant nomenclature than to animal nomenclature in most respects, particularly in author citation style, where and is used rather than the Latin et. When writing about organisms across multiple kingdoms in the same manuscript, check each name against its own governing code rather than applying one set of rules universally.

Key Style Guide References for Bacterial Names

No single style guide covers every situation in bacterial nomenclature. The right reference depends on your field and target journal. Always check your journal’s author instructions first, as these override general style guides.

Style Guide Comparison

Primary Nomenclature Resources

• LPSN (List of Prokaryotic names with Standing in Nomenclature): bacterio.net
• IJSEM (International Journal of Systematic and Evolutionary Microbiology): publishes all Notification and Validation Lists
• EzBioCloud: searchable database of validly published prokaryotic names

Quick-Reference Checklist Before Submission

We have a free checklist you can use to verify you’ve correctly present bacterial names in your manuscript, before submitting it to a journal: Bacterial_names_submission_checklist

Frequently Asked Questions

Do bacterial names need to be italicized in tables and figures?

Yes. Italicization applies throughout the manuscript, including table cells, figure legends, and captions. The first-mention rule also applies independently in each legend — write the full name in italics the first time it appears in a legend, even if it has already been abbreviated in the main text.

What does it mean when a bacterial name is in quotation marks?

Quotation marks indicate that a name has been effectively published, meaning it has appeared in the scientific literature, but has not yet been validly published through the IJSEM Notification or Validation List process. These names lack official standing in nomenclature and should be used with caution. Example: “Selenomonas massiliensis.”

How do I know if a bacterial name is currently valid?

Check the List of Prokaryotic names with Standing in Nomenclature (LPSN) at bacterio.net, or search EzBioCloud at ezbiocloud.net. Both databases are updated regularly to reflect Notification and Validation Lists published in IJSEM. Do not rely on a name simply because it appears in a recent publication because publication alone does not confer validity.

Should I use the old name or the new name when a bacterium has been reclassified?

Use the currently accepted valid name, then note the former name in parentheses on first mention, for example, Helicobacter pylori (formerly Campylobacter pylori). Check your target journal’s author instructions, as some journals specify a preferred nomenclatural authority. When community consensus on a reclassification is still contested, acknowledge both names and cite the relevant taxonomic proposals.

Are gene names formatted the same way as species names?

No. Gene names follow different rules. Bacterial gene names use a three-letter lowercase italic abbreviation (e.g., hisA, recA), sometimes followed by an uppercase letter when multiple genes share a function. Phenotype designations derived from gene names are written in roman (non-italic) text with an initial capital (e.g., His⁻, Rec⁺). These conventions are governed by journal-specific style guides, most notably the ASM Style Manual, not the Prokaryotic Code.

References

[1] CSE, Style Manual Committee. 2014. Scientific Style and Format: the CSE manual for authors, editors, and publishers, 8th edn, p. 401. Wheat Ridge, Colorado, USA: Council of Science Editors. 722 pp.

[2] Piqueras M and Guerrero R. 2013. Bacteriological nomenclature, pp. 59–62 in Science Editor’s Handbook, 2nd edn. edited by P Smart, H Maisonneuve, and A Polderman. Redruth, Cornwall, UK: European Association of Science Editors. 231 pp.

[3] AMA. 2007. AMA Manual of Style: a guide for authors and editors, 10th edn., pp. 748–753. New York: Oxford University Press [and American Medical Association]. 1010 pp.