Identification and Characterization of Rothia amarae sp. nov. in a Suspension Culture of Arabidopsis thaliana (Heynh.) Cells

Abstract

We report for the first time that a nonpathogenic bacterial microflora has been found in a suspension culture of Arabidopsis thaliana cells. The 16S rRNA gene sequencing showed that the isolate belonged to Rothia amarae. Identification was confirmed by microbiological, microscopic, and immunochemical methods. Growth of the isolate on blood agar preserves the morphological and immunochemical properties of the isolate from the plant cell suspension culture. Whether the isolated strain is a contaminant or a true symbiont remains an open question. It is known that Rothia bacteria live mostly in oceanic and waste water and in benthos. Members of Rothia are part of the normal microflora of the oral cavity, respiratory tract, and stomach of humans. Endophytic Rothia are inhibitory against several pathogenic fungi and bacteria. In addition, some actinobacteria, including members of Rothia, are nitrogen fixers. It cannot be ruled out that the R. amarae strain isolated in this work can be endosymbiotic with a suspension culture of A. thaliana. The bacterial "inclusions" found by us in a suspension culture of A. thaliana merit further investigation to identify them more deeply and clarify their symbiotic properties.

Elimination of contamination in the published 16S rRNA gene sequence ofRothia amaraetype strain J18Tduring phylogenetic studies of a bacterial isolate from a suspension cell culture ofArabidopsis thaliana(Heynh.)

“…This type strain, described in (Fan et al . 2002), was isolated from a foul water sewer in Beijing, China, and was described as a Gram-positive bacterium that forms coccoid cells with a diameter of 0.6–0.9 μm, in agreement with the description of Isolate SG in Sokolov et al . (2021).…”

“…Phylogenetic studies of our bacterial isolate (Isolate SG) from an Arabidopsis suspension culture (Sokolov et al . 2021) by using MSAs and comparisons of the SSU rRNA secondary structures have provided convincing evidence for contamination of the published 16S rRNA gene sequence of R. amarae type strain J18 T (GenBank AY043359.1).…”

“…In a suspension culture of Arabidopsis thaliana (L.) Heynh (All-Russian Collection of Higher Plant Cell Cultures, Timiryazev Institute of Plant Physiology of the Russian Academy of Sciences, Moscow, Russia), we found the presence of a bacterial microflora (Sokolov et al . 2021) that did not have a suppressing effect on the plant.…”

Phylogenetic Analysis of a Bacterial Strain of the GenusRothiaDetected in Suspension Culture Cells ofArabidopsis thaliana(L.) Heynh as a Member of the FamilyMicrococcaceae

“…Endophytic Rothia strains of different species have been isolated from the rhizosphere and tissues of the following plants: Sphagnum magellanicum (Opelt et al, 2007), Dysophylla stellata (Xiong et al, 2013), Hedysarum perrauderianum, H. naudinianum (Torche et al, 2014), Musa acuminate (Sekhar and Thomas, 2015), Oryza sativa (Evangelista et al, 2017), Seidlitzia rosmarinus (Shurigin et al, 2020), Camellia sinensis (Borah and Thakur, 2020), Alnus glutinosa (Davis et al, 2020), A. incana (Mercurio et al, 2022), Zea mays (Pisarska and Pietr, 2015;Elbahnasawy et al, 2021), Vaccinium myrtillus (Mažeikienė et al, 2021), Santalum album (Tuikhar et al, 2022), Miscanthus floridulus (Xiao et al, 2023), and Arabidopsis thaliana (Sokolov et al, 2021). Rothia endophytes are inhibitory to several pathogenic fungi, bacteria, parasitic nematodes, and insect larvae, and they can be used as biofertilizers (Bano and Muqarab, 2017;da Silva et al, 2018;Asadu et al, 2020;Nuaima, 2022).…”

“…Analysis of the systematic position of Isolate SG (Sokolov et al, 2021) and the phylogenetic studies of Rothia members in the 16S rRNA-based test (Xiong et al, 2013;Elbahnasawy et al,2021;Tuikhar et al, 2022;de Oliveira et al, 2022;Fatahi-Bafghi, 2021;Stubbendieck et al, 2023;Yastrebova and Plotnikova, 2020;Fan et al, 2002;Ko et al, 2009) have shown their taxonomic proximity to other Micrococcaceae, including Kocuria, Arthrobacter, Micrococcus, and other genera.…”