Do “Bacterial Mitochondria” Exist? A Bibliometric Assessment
2026 年 18 巻 p. 24-28
詳細
2026 年 18 巻 p. 24-28
In basic biology, it is well known that bacteria do not contain mitochondria, while eukaryotic cells contain mitochondria of prokaryotic origin. Despite this, some literature states that bacteria do have mitochondria. To quantitatively assess the presence of the term “bacterial mitochondria” in Crossref DOI-indexed journals, Google Scholar and PubPeer were sourced on 25 February 2026 and screened, limiting the dataset primarily to literature published in 2021–2026. A total of 64 texts were manually verified as carrying a single mention of “bacterial mitochondria” in their PDF texts. While 43 texts indicated a source, 21 did not. Only four of the 43 sources also used the term “bacterial mitochondria”. Unless robust and irrefutable proof is provided by the microbiological community that bacteria harbor mitochondria—thereby revolutionizing existing basic biological knowledge—the scientific, peer-reviewed literature that was assessed in this analysis can be assumed to contain statements of factual error, negatively impacting their use in biology education as accurate or reliable sources of knowledge.
In classic biology, the mitochondrion is an organelle that is typically associated with eukaryotic multicellular organisms (e.g., plants and animals) as well as eukaryotic unicellular organisms (e.g., unicellular algae and ‘protozoans’). Mitochondria are of evolutionarily claimed bacterial ancestry, and have several functions, the core one being the supply of energy to a cell, in the form of ATP (Al Amir Dache and Thierry, 2023). Plant mitochondria were first discovered toward the latter part of the 20th century (Ernster and Schatz, 1981), but in the 1950s, Mudd (1953) coined the concept of “mitochondria of bacteria” to describe particulate structures in bacteria that visually resembled eukaryotic mitochondria, as had been identified in about three dozen studies dating from 1940 to 1953 that had presented morphological, ultrastructural (electron micrographic) and other evidence to support that claim 1. However, most citations to the Mudd (1953) paper were in articles published in the 1950s and 1960s, at least according to Google Scholar 2, suggesting that the hypothesis put forward by Mudd has not gained traction or accumulated any robust scientific evidence to support the existence of “mitochondria of bacteria” in the past 70 years. Part of that historical evolutionary trajectory of mitochondrial research has involved a concerted effort to identify their protobacterial origin (Pontieri et al., 2015).
It is thus assumed in this article that until robust evidence is presented by researchers that proves otherwise, that “bacterial mitochondria”—at least based on physiological, cytological, biochemical, histological, microscopic, and metabolic characteristics that define these organelles in eukaryotes—do not exist in bacteria (i.e., prokaryotic microorganisms).
To the author’s understanding, there are three fundamental aspects of biology education, as might occur in schools or higher educations, such as universities: 1) to ensure the veracity of knowledge that is being taught, 2) to probe the scientific source of such information—such as indexed scientific journals—and 3) that the pedagogical vehicles or agents of knowledge transmission—primarily teachers, educators, and lecturers—accurately transmit scientifically verified information to their students. Much effort has been invested in the cognitive and conceptual framework of biology education (Nehm, 2019). Educators of biology—as well as biologists themselves—are intellectually free to expand existing conceptual frameworks by accommodating novel scientific theorems, provided that such scientific novelties have a sound scientific basis. However, as exemplified in this article, inaccurate knowledge—even more so when labelled as scientific and appearing in journals that claim to be peer-reviewed—diminishes the evidence-based nature of science (Inêz et al., 2023) because the fundamental principle of truth is distorted or violated (Barzilai and Chinn, 2020).
A bid was made to identify indexed literature—defined here as an article published in a journal that claims to be peer-reviewed, and digitally archived using a digital object identifier (DOI), as recognized by Crossref3—containing the term “bacterial mitochondria”. A search for this term was conducted at Google Scholar on 25 February 2026 (Google Scholar, 2026), restricting the publication date to recent years (2021–2026). This term was identified in articles’ PDF files using Adobe Acrobat Reader. The 94 results that were discovered were manually screened between 25 February and 1 March 2026, and any results for which full texts could not be obtained or false positives, duplicates, book chapters, theses, or any other document type without a Crossref DOI (preprints, on the other hand, were considered, if applicable), as well as any non-English texts, were excluded.
To supplement and fortify this search, the post-publication portal PubPeer was sourced on 25 February 2026 (PubPeer, 2026) to identify any additional cases of peer-reviewed DOI-assigned articles, published from 2021–2026, with the term “bacterial mitochondria”. The initial 93 results were manually screened between 25 February and 1 March 2026 to exclude false positives and articles in which figures of bacterial cells included mitochondria, while only including articles in which the term “bacterial mitochondria” (or close derivatives e.g., “bacterial mitochondrial”) appeared.
In the full texts that were examined (n = 64), the verbatim statements containing “bacterial mitochondria” were recorded, as were their location (page) within the text. In addition, the sources of the claim, as indicated by the in-text citations that appeared in the reference lists of those articles, were assessed to verify the presence of the term “bacterial mitochondria” (see “Source literature” sheet in the Suppl. file). Moreover, any source texts that mentioned the term “bacterial mitochondria” and provided a source for that claim, were also recorded and assessed (see “Source of source literature” sheet in the Suppl. file).
After applying these filters and removing duplicates from the 94 initial Google Scholar results and the 93 PubPeer results, while screening the full texts to confirm the presence of “bacterial mitochondria” between 25 February and 1 March 2026, a total of 64 cases published in 2021–2026 were identified in the Google Scholar and PubPeer datasets, 51 of which were not annotated at PubPeer (Suppl. file).
A detailed examination of these cases reveals that the vast majority (97%)4 used the term “bacterial mitochondria” only once in the text, usually to describe some negative reaction to bacterial cells in response to an abiotic stressor, such as silver (e.g., silver nanoparticles). In other words, except for the support of this term by citing literature from the mid-20th century, more recent (2021–2026) articles did not appear to provide any scientific evidence to support the claim that “bacterial mitochondria” exist. Surprisingly, many of these articles were published in journals that are generally deemed to be robustly peer reviewed, and published by publishers that are typically deemed to be defenders of information integrity, such as Elsevier (18 cases) or Springer Nature (9 cases). Among the authors’ country affiliations of these papers, China (19) and India (10) ranked first and second. However, the presence of this term in these peer-reviewed sources suggests that peer review (and editorial verification) was not as careful as it should have been, even though it is generally understood that authors are the agents ultimately responsible for the content of their articles.
Of the 64 full texts examined5, 43 indicated a source6, i.e., the cited literature also used the term “bacterial mitochondria”, while 21 texts did not indicate any source of their claim (Suppl. file). Of the 43 sources examined, only four employed this term while 39 did not (see “Source literature” sheet in Suppl. file). Of the four sources that used the term, three cited literature sources (n = 4) that did not use this term (see “Source of source literature” sheet in Suppl. file). In other words, in the 64 articles examined, two bibliometric “generations” of citations were identified that claimed the existence of “bacterial mitochondria”, i.e., 67% (43/64) of the 64 peer-reviewed documents (first “generation” of citation) and 9.3% (4/43) of the “first generation” sources (i.e., second “generation” of citation), together spanning source literature ranging from between 1991 and 20257. In one distinct case (DOI: 10.1016/j.jallcom.2025.185275), the authors claimed to have used a commercial kit to assay metabolic activity in “bacterial mitochondria”.
From a biological education perspective, as was noted above, truth forms a central epistemological basis of scientific knowledge (Fuselier et al., 2019). Thorough trust is placed—often blindly—in the scientific validity of any knowledge found in journals that claim to be peer reviewed, even when—as evidenced by the 64 cases shown in this article’s exercise—that truth can be “twisted” to convey the existence of a stated and peer-reviewed fact—i.e., the existence of “bacterial mitochondria”—that has yet to be scientifically proved. This excludes claims of their existence made over 70 years ago (Mudd, 1953) that appear to have been based on about three dozen sources which may have presented scientific evidence that in modern-day science might be considered as weak or vestigial. In other words, in the 64 articles that appear in peer-reviewed journals—including of publishers that are traditionally perceived as being trustworthy—an untruthful claim (also a statement of fact) is being made, namely that “bacterial mitochondria” exist. Furthermore, these 64 documents cite 46 sources of this concept, even though most of those sources did not use the term “bacterial mitochondria”.
It may be all too easy to attempt to offer a simplistic explanation to somehow justify the existence of these errors in these documents, such as by ascribing it to authors’ descriptive carelessness, or the oversight of peer reviewers and editors. However, the errors persist and the documents remain publicly available for scientists and educators alike to use, cite, and interpret. When an untruthful fact is used to base educational arguments, such as in school classes or university course work, this then violates a fundamental epistemological basis of science education, allowing it to be falsified (Morante and Rossi, 2016). The veracity of knowledge related to both the fields of mitochondria and bacteria risks being corrupted, even if it is currently limited to around 64 verified texts, because this knowledge is made more discoverable, such as on publicly open platforms like Google Scholar, and via their digital identifiers, like DOI. In all cases where the source did not employ the term “bacterial mitochondria”, it can be argued that the citing document has miscited the source. In such cases, the miscited authors have the right to not be inaccurately cited (Teixeira da Silva and Vuong, 2021, 2023).
The main objective of this article is to make readers and the wider biological community—especially the niche of microbiological researchers—aware that at least in 64 peer-reviewed and DOI-indexed articles, bacteria are indicated as having mitochondria, even if those articles do not provide proof, or even if they merely cited another source that made that claim, without proof. Although this is not an accusation of misconduct, it does raise doubts about the scientific veracity of such a fundamental biological claim. This is because the free use of “bacterial mitochondria” in science literature as part of published articles is tantamount to a public endorsement of the validity of the concept. The claim that “bacterial mitochondria” exist remains for researchers to discover and present robust, irrefutable evidence. If found to be true, then a major fundamental basis of basic biology—especially microbiology—would need to be adjusted in textbooks and a wide swathe of scientific literature. Even as this cautious note is made, there may be those who argue that the risk to the epistemological truth–trust axis is limited since “bacterial mitochondria” are mentioned only once in 97% of the 64 texts.
Author’s contributions: Conceptualization, investigation, verification, writing, editing. No AI was used for any of these functions.
Competing interests: None.
Funding: None.
Availability of data and material: Source bibliometric data can be found in the Suppl. file which can be found at Zenodo: https://doi.org/10.5281/zenodo.20602249
Ethics approval and consent to participate: Not applicable.
Consent for publication: Not applicable.
1Those source documents cited by Mudd were not examined to ascertain the validity of the claims, or to examine their evidence provided, and the statements, descriptions and summaries provided by Mudd were taken at word.
2https://scholar.google.co.jp/scholar?cites=1225876465696376722&as_sdt=2005&sciodt=0,5&hl=en
3Identified at: https://search.crossref.org/
4There were two exceptions (DOI: 10.1371/journal.pbio.3002723; 10.1155/2021/1341604), which had two mentions of “bacterial mitochondria” each.
5Limitation: A search with no date restrictions revealed approx. 260 results at Google Scholar on 25 February 2026: https://scholar.google.co.jp/scholar?hl=en&as_sdt=0%2C5&q=%22bacterial+mitochondria%22&btnG=
6With a total of 46 sources indicated, one being untraceable. One of the sources (DOI: 10.1016/j.nano.2015.11.016) was cited by four of the 64 documents analyzed.
7Limitation: The citation of scientific support, explanation, or evidence of this phenomenon was not examined, but a future study that examines cascading “generations” of citations to attempt to identify the exact sources of the initial concept, as well as the different lines of evidence that were cited to claim the existence of “bacterial mitochondria”, is warranted.
