Title
Short communication Growth of dairy isolates of Geobacillus thermoglucosidans in skim milk depends on lactose degradation products supplied by Anoxybacillus flavithermus as secondary species
Author
Zhao, Y.
Kumar, M.
Caspers, M.P.M.
Nierop Groot, M.N.
van der Vossen, J.M.B.M.
Abee, T.
Publication year
2018
Abstract
Thermophilic bacilli such as Anoxybacillus and Geobacillus are important contaminants in dairy powder products. Remarkably, one of the common contaminants, Geobacillus thermoglucosidans, showed poor growth in skim milk, whereas significant growth of G. thermoglucosidans was observed in the presence of an Anoxybacillus flavithermus dairy isolate. In the present study, we investigated the underlying reason for this growth dependence of G. thermoglucosidans. Whole-genome sequences of 4 A. flavithermus strains and 4 G. thermoglucosidans strains were acquired, with special attention given to carbohydrate utilization clusters and proteolytic enzymes. Focusing on traits relevant for dairy environments, comparative genomic analysis revealed that all G. thermoglucosidans strains lacked the genes necessary for lactose transport and metabolism, showed poor growth in skim milk, and produced white colonies on X-gal plates, indicating the lack of β-galactosidase activity. The A. flavithermus isolates scored positive in these tests, consistent with the presence of a putative lactose utilization gene cluster. All tested isolates from both species showed proteolytic activity on milk plate count agar plates. Adding glucose or galactose to liquid skim milk supported growth of G. thermoglucosidans isolates, in line with the presence of the respective monosaccharide utilization gene clusters in the genomes. Analysis by HPLC of A. flavithermus TNO-09.006 culture filtrate indicated that the previously described growth dependence of G. thermoglucosidans in skim milk was based on the supply of glucose and galactose by A. flavithermus TNO-09.006. Chemicals / CAS lactose, 10039-26-6, 16984-38-6, 63-42-3, 64044-51-5; Lactose.
Subject
symbiosis
thermophile
thermoresistant spore
Anoxybacillus
bovine
dairy product
genetics
Geobacillus
growth, development and aging
isolation and purification
metabolism
microbiology
Animals
Anoxybacillus
Cattle
Dairy Products
Geobacillus
Lactose
Milk
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http://resolver.tudelft.nl/uuid:887ba38c-f42c-4966-bde2-39d90ddfde68
DOI
https://doi.org/10.3168/jds.2017-13372
TNO identifier
955014
ISSN
0022-0302
Source
Journal of Dairy Science, 101 (101), 1013-1019
Document type
article