A tridecaptin-based fluorescent probe for differential staining of Gram-negative bacteria
The traditional Gram-staining method, which was invented more than a century ago for differentiating bacteria as Gram positive or Gram negative, is still widely practiced in microbiology. However, Gram staining suffers from several problems which can affect the accuracy of the diagnosis. Here, we report a new Gram-negative-specific fluorescent probe, which is based on a narrow-spectrum antibiotic, tridecaptin A1, and allows selective staining of Gram-negative bacteria in different fixed bacterial samples. Solid-phase peptide synthesis was used to prepare the tridecaptin A1–fluorophore conjugate with a single structure. Labeling selectivity of the probe toward Gram-negative bacteria was confirmed by testing against a panel of bacterial species. By combining the use of a previously reported Gram-positive-specific fluorescent probe, we then further showed the capability of the new probe in differential labeling of a number of complex bacterial samples, which included a mouse gut microbiota cultured in vitro, as well as microbiotas collected from the human oral cavity, soil, and crude oil. High labeling selectivity and coverage were observed in most samples. This method offers a new Gram-negative-specific probe with a defined structure, which allows facile fluorescence-based differentiation of Gram-positive and Gram-negative bacteria for further microbial studies.
KeywordsMicrobiota imaging Gram staining Tridecaptin A1 Differential bacterial labeling Antibiotic-based probe
This work is supported by the National Natural Science Foundation of China (21735004, 21775128, 21705024, 21807070).
Compliance with ethical standards
Oral microbiota donor had given informed consent for the experiment. All animal experiments were carried out in accordance with guidelines approved by the Institutional Animal Care and Use Committee of the Shanghai Jiao Tong University School of Medicine, and the use of human microbiota samples was approved by the Ethics Committee at Renji Hospital of Shanghai Jiao Tong University School of Medicine.
Conflict of interest
The authors declare that they have no conflict of interest.
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