The honey crop, with its constant nectar flow, high osmotic pressure, and presence of microorganisms introduced by foraging is the ideal environment for these systems

to be activated. These systems in these conditions rely on specific gene expressions in different cell processes, such as extra-cellular proteins and peptides, to deal with these harsh environmental conditions [19]. In general, LAB can produce great amounts of cell surface and extra-cellular proteins such as bacteriocins, molecular chaperones, enzymes, lipoproteins, and surface layer proteins [6, 20] that are involved in varying cell processes. Surface layer or extracellular proteins are essential CHIR98014 mouse for niche Luminespib mouse protection, and their survival forms part of the proteome known as the “secretome” [21]. From

our previous research we have seen that these symbiotic LAB species possess antimicrobial properties against bee learn more pathogens and other microorganisms introduced by nectar foraging and they work together synergistically as a defense system [15, 18]. In this work we investigate whether this activity could be attributable to any secreted proteins. To that end, we identify extra-cellular proteins from each Lactobacillus and Bifidobacterium spp. from the honey crop separately under microbial stress in order to understand their ecological roles as antimicrobial barriers against incoming threats and their roles in honey production. Results The honey crop Lactobacillus Fhon13N, Biut2N, Hma8N, Bin4N, Hon2N, Hma11N, Hma2N, Bma5N, and Lacobacillus kunkeei Fhon2N have genome sizes ranging from 1.5 to 2.2 Mbps, and the number of predicted proteins ranges from 1330 to 2078 (Table  1). The fraction of predicted proteins in these strains with known function is on average 71%, the fraction without known function but similar to other known proteins is on average of 26%, and proteins without known function or similarity are on average 4%. The honey crop Bifidobacterium Bin2N, Bin7N,

Hma3N, and Bifidobacterium coryneforme Bma6N have genome sizes ranging from 1.7 to 2.2 Mbps, and the number of predicted proteins ranges from 1386 to 1836 (Table  1). The fraction of predicted proteins in Bin2N, Bin7N, Hma3N, and B. Parvulin coryneforme Bma6N with known function is on average 69%, without known function but similar to other known proteins is on average 26%, and proteins without known function or similarity are on average 5%. Further genomic data and analysis on these 13 LAB species will be covered in full detail in another paper. Table 1 Genomic characteristics of the 13 LAB symbionts from the honey crop   Genome size (Mb) Total ORFs ORFs – with assigned function (%) ORFs – without assigned function, with similarity (%) ORFs – no similarity or assigned function (%) Lactobacillus           Fhon13N 1.5 1 330 72 25 4 Fhon2N 1.6 1 504 73 24 3 Bin4N 1.