| Congresso Brasileiro de Microbiologia 2023 | Resumo: 790-1 | ||||
Resumo:In recent years, there has been an increasing interest in investigating the cause of anomalous blue discoloration in various foods, especially dairy products. Strains of the genus Pseudomonas, in particular, those belonging to the Pseudomonas fluorescens group have been associated with the occurrence of discoloration in cheeses. Pseudomonas are bacteria naturally widespread in the environment, they are rod-shaped, aerobic, Gram-negative, non-spore forming, some species are pathogenic for humans, animals, or plants, and several members produce pigments. Therefore, our aim was to identify the cause of blue discoloration in the processed cheese “Requeijão em Barra”, from a dairy industry located in the state of Minas Gerais, Brazil, which was reported in 2020. Samples that exhibited blue discoloration were analysed, and presumptive isolates for Pseudomonas were obtained by plating on Pseudomonas agar base supplemented with cephaloridine, fucidin, cetrimide (CFC), and bromothymol blue (0.02 g L-1), with incubation at 25 °C for 48h. Isolates were tested for catalase, oxidase, and Gram staining. Then, they were tested to pigment producing in Pseudomonas minimal medium (PMM), with 30 mM glucose as a carbon source. The test was conducted in 24-well cell culture plates, at 10, 25 and 32 °C for 10 days. Furthermore, the isolates have been confirmed at the genus level by PCR amplification of the genus-specific region of 16S rRNA. The genetic variability between them was analysed by rep-PCR, and based on the obtained profiles and similarities, one isolate (RQ057) producing blue pigment was selected for whole-genome sequencing and genomic analysis. The RQ057 was identified as Pseudomonas paracarnis using the in-silico DNA-DNA hybridization, ANIb calculation, and by TYGS web server. The strain exhibited blue pigment production in PMM at 10 °C and 25 °C after 4 and 2 days, respectively, but no blue pigment at 32 °C for 10 days. In its draft genome, pyoverdine biosynthetic clusters, integrative and conjugative elements (ICE), prophage regions, and genomic islands (GIs) were predicted. Furthermore, copies of genes related to the tryptophan biosynthetic pathway (trpCBAFD), exclusive to strains causing blue discoloration, are contained in the region identified as ICE and which was also identified in GIs. This finding suggests that, at some point in evolution, this region may have been transferred between different bacteria, enabling the dissemination of the set of genes associated with blue discoloration. Hence, a comprehensive characterization of genomic regions in food-related strains can stimulate advancements in detection methods.
Palavras-chave: Blue discoloration, Cheese spoilage, Genomic analysis, Pseudomonas Agência de fomento:CAPES, CNPq, FAPEMIG | |||||