Macrococcus animalis sp. nov. and Macrococcus equi sp. nov., isolated from different animals’ origins.

Overview

• This research article describes the identification and characterization of two new bacterial species, Macrococcus animalis sp. nov. and Macrococcus equi sp. nov., which were isolated from various animal sources.
• These species were differentiated from closely related bacterial species using genomic, biochemical, and chemotaxonomic analyses, confirming their novelty.

Detailed Explanation

Isolation and Sources

• Researchers isolated nine strains of Gram-positive, non-motile, facultatively anaerobic cocci.
• The samples were collected from different animals and sites, including:
  • Horse and pig skin
  • Bovine mastitis milk
  • Feline urine from a urinary tract infection
• The strains were designated with identifiers EM39Eᵀ, JEK85, 18KM676, 21M1142, 18KM445, 18KM444, 18KM245, 18KM583, and 21KM1573.

Phylogenomic and Genomic Analysis

• Whole-genome sequencing was performed and amino acid alignments were used for phylogenomic analysis.
• Digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) were calculated to assess genetic relatedness.
• Gene comparisons involving the 16S rRNA and protein-coding genes such as rpoB, tuf, and sodA were conducted.
• MALDI-TOF MS spectral profiles also supported placement within the Macrococcus clade.
• Comparisons were made with closely related reference strains: CCM 7100ᵀ, CCM 7099ᵀ, CCM 4927ᵀ, and DSM 113939.
• Key genomic distances observed:
  • The two novel species shared 22.30% dDDH and 79.49% ANI between each other, below the species threshold indicating separation.
  • Both novel species showed less than 24% dDDH and 82% ANI when compared to their closest relatives, which is also below threshold limits for known species.

Chemotaxonomic Features

• Polar lipids analysis identified:
  • Diphosphatidylglycerol
  • Phosphatidylglycerol
  • Aminolipids
  • Glycolipids
  • Phosphoglycolipids
• Fatty acid profiles showed major fatty acids such as:
  • C14:0 (myristic acid)
  • C18:1 ω11c (oleic acid isomer)
  • C15:0 (pentadecanoic acid)
  • C18:1 ω13c
  • Anteiso-C15:0 was detected in one species, indicating subtle chemotaxonomic differences.
• The peptidoglycan type in the cell wall was classified as A3α l-Lys-Gly2.

Phenotypic and Biochemical Distinctions

• Growth in high salt concentrations (12.5% NaCl) distinguished the novel species from their closest relatives.
• Differentiation within the two novel species was based on:
  • Ability to metabolize d-ribose: species EM39Eᵀ, JEK85, 18KM676, and 21M1142 tested positive.
  • Absence of β-glucosidase activity and lack of acid production from methyl-β-D-glucopyranoside and maltose: shown by strains 18KM445, 18KM444, 18KM245, 18KM583, and 21KM1573.
  • These biochemical traits allowed distinguishing between Macrococcus animalis and Macrococcus equi.

Taxonomy and Strain Designation

• The strains formed two distinct clusters fulfilling criteria for novel species status.
• The cluster including strains 18KM445, 18KM444, 18KM245, 18KM583, and 21KM1573 was designated Macrococcus animalis sp. nov.
• The type strain for M. animalis is 18KM445ᵀ (deposited as DSM 118744ᵀ, CCOS 2124ᵀ, CCM 9438ᵀ).
• The second cluster including EM39Eᵀ, JEK85, 18KM676, and 21M1142 was designated Macrococcus equi sp. nov.
• The type strain for M. equi is EM39Eᵀ (deposited as DSM 118743ᵀ, CCOS 2125ᵀ, CCM 9439ᵀ).
• The “sp. nov.” notation indicates these are newly described species.

Significance

• This study expands the taxonomy of the genus Macrococcus by adding two new species isolated from distinct animal hosts and clinical/environmental sources.
• The multi-faceted approach combining genomic, chemotaxonomic, and phenotypic data strengthens the evidence for defining novel bacterial species.
• Understanding these species contributes to better knowledge of animal microbiota and potential pathogens involved in animal infections.