Identification of Pseudomonas asiatica subsp. bavariensis str. JM1 as the first Nε -carboxy(m)ethyllysine-degrading soil bacterium.

Thermal food processing leads to the formation of advanced glycation end products (AGE) such as Nε -carboxymethyllysine (CML). Accordingly, these non-canonical amino acids are an important part of the human diet. However, CML is only partially decomposed by our gut microbiota and up to 30% are excreted via faeces and, hence, enter the environment. In frame of this study, we isolated a soil bacterium that can grow on CML as well as its higher homologue Nε -carboxyethyllysine (CEL) as sole source of carbon. Bioinformatic analyses upon whole-genome sequencing revealed a subspecies of Pseudomonas asiatica, which we named 'bavariensis'. We performed a metabolite screening of P. asiatica subsp. bavariensis str. JM1 grown either on CML or CEL and identified N-carboxymethylaminopentanoic acid and N-carboxyethylaminopentanoic acid respectively. We further detected α-aminoadipate as intermediate in the metabolism of CML. These reaction products suggest two routes of degradation: While CEL seems to be predominantly processed from the α-C-atom, decomposition of CML can also be initiated with cleavage of the carboxymethyl group and under the release of acetate. Thus, our study provides novel insights into the metabolism of two important AGEs and how these are processed by environmental bacteria.

Population structure of Borrelia turcica from Greece and Turkey.

Borrelia turcica, a member of the reptile-associated Borrelia clade, is vectored by Hyalomma aegyptium. The only suggested reservoir hosts of B. turcica are tortoises of the genus Testudo. Borrelia turcica has been described to occur in several Southeastern European countries including Turkey, Romania, Bulgaria and Greece but so far nothing is known about the relationship of these populations and whether or how they are structured. Using multilocus sequence typing (MLST) on eight chromosomally located housekeeping loci (clpA, clpX, nifS, pepX, pyrG, recG, rplB and uvrA) we analyzed 43 B. turcica isolates from Serres, Greece (n = 15) collected in 2017 and Izmir, Turkey (n = 28) collected in 2018. To understand their relationship a maximum-likelihood phylogenetic tree and goeBURST analysis were done based on MLST sequence data and allelic profiles, respectively. The data we generated confirmed that the samples of B. turcica investigated here were divergent from Lyme disease (LD) and relapsing fever (RF) species. Within the B. turcica clade, samples of different geographic origin (Greece, Turkey) clustered together in terminal branches; no obvious differences between the Greek and Turkish samples were noticeable. A goeBURST analysis using triple-locus variants revealed very few clonal complexes with the majority of samples appearing as singletons. Minor clonal complexes (consisting of two sequence types) comprised only Greek isolates, only Turkish isolates or both, so no pattern of clustering of isolates from the two geographical regions was observed. Interestingly, very little population structure was discerned in our study. This was surprising in view of the large geographic distance between collection sites of B. turcica and raises questions about the evolution or spatial spread of this species.