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Updated: Dec 28, 2025
Evaluation of Microbial Safety of Dairies using Bacterial Proteomic Profiling via MALDI Approach
Published on: October 7, 2025
Pseudomonas haemolytica sp. nov., isolated from raw milk and skimmed milk concentrate
Katharina Hofmann1, Christopher Huptas1, Etienne V Doll1
1Chair of Microbial Ecology, ZIEL - Institute for Food & Health, Technische Universität München, Weihenstephaner Berg 3, 85354 Freising, Germany.
Abstract:
Two strains, WS 5063T and WS 5067, isolated from raw cow's milk and skimmed milk concentrate, could be affiliated as members of the same, hitherto unknown, Pseudomonas species by 16S rRNA and rpoD gene sequences. Multilocus sequence and average nucleotide identity (ANIm) analyses based on draft genome sequences confirmed the discovery of a novel Pseudomonas species. It was most closely related to Pseudomonas synxantha DSM 18928T with an ANIm of 91.4 %. The DNA G+C content of WS 5063T was 60.0 mol %. Phenotypic characterizations showed that the isolates are rod-shaped, motile, catalase- and oxidase-positive, and aerobic. Growth occurred at 4-34 °C and at pH values of pH 5.5-8.0. Both strains showed strong β-haemolysis on blood agar. The major cellular polar lipids were phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol. The dominant quinone was Q-9 (90 %), but noticeable amounts of Q-8 (9 %) and traces of Q-7 were also detected. Fatty acid profiles were typical for Pseudomonas species and exhibited C16 : 0 as a major component. Based on these results, we conclude that both strains belong to a novel species, for which the name Pseudomonas haemolytica sp. nov. is proposed. The type strain is WS 5063T (=DSM 108987T=LMG 31232T) and an additional strain is WS 5067 (=DSM 108988=LMG 31233).
Insights
A novel Pseudomonas species, Pseudomonas haemolytica, was discovered in raw milk products. This bacterium exhibits strong beta-hemolysis and unique genetic and phenotypic characteristics, expanding our understanding of dairy-associated microbes.
Area of Science:
- Microbiology
- Genomics
- Dairy Science
Background:
- The genus *Pseudomonas* comprises diverse bacteria found in various environments, including dairy products.
- Identification and characterization of novel species are crucial for understanding microbial ecosystems and potential applications.
Purpose of the Study:
- To identify and characterize a previously unknown *Pseudomonas* species isolated from raw cow's milk and skimmed milk concentrate.
- To establish the taxonomic and phylogenetic position of the novel isolates within the *Pseudomonas* genus.
Main Methods:
- 16S rRNA and *rpoD* gene sequencing for initial identification.
- Multilocus sequence analysis (MLSA) and average nucleotide identity (ANIm) using draft genome sequences.
- Phenotypic characterization including growth conditions, biochemical tests, and hemolysis assays.
- Analysis of polar lipids, quinones, and fatty acid profiles.
Main Results:
- Two strains, WS 5063T and WS 5067, were identified as a novel *Pseudomonas* species based on phylogenetic analyses.
- The novel species is most closely related to *Pseudomonas synxantha* with an ANIm of 91.4%.
- The isolates are aerobic, motile rods, positive for catalase and oxidase, exhibiting strong β-hemolysis and specific growth ranges (4-34°C, pH 5.5-8.0).
- Major polar lipids included phosphatidylethanolamine, phosphatidylglycerol, and diphosphatidylglycerol; the dominant quinone was Q-9.
- Fatty acid profiles were typical for *Pseudomonas*, with C16:0 as the major component.
Conclusions:
- The two isolates represent a novel species, *Pseudomonas haemolytica* sp. nov.
- The type strain is WS 5063T (=DSM 108987T=LMG 31232T).
- This discovery contributes to the taxonomic diversity of the *Pseudomonas* genus in dairy environments.
