Diversity, antimicrobial production, and seasonal variation of honey bee microbiota isolated from the honey stomachs of the domestic honey bee, Apis mellifera

The antimicrobial nature of honey and its related apiological origins typically focus on basic chemical analysis without attempting to understand the diversity of the microbial component. The antibacterial activity, chemical characterization, and diversity of bacteria isolated from Apis mellifera honey stomachs and hive honey collected throughout the honey production season are presented. After screening >2,000 isolates, 50 isolates were selected and characterized by 16S rRNA gene homology, Gram stain, catalase and protease tests, as well as for antibacterial activity against select indicators. Antibacterial-producing isolates were predominantly from the Pseudomonas, Paenibacillus, Lonsdalea, Serratia, and Bacillus genera. Isolates collected from honey stomachs in April displayed the highest level of activity (27%). While April isolates did not demonstrate activity against the Gram-negative bacteria tested. Whereas 59% of July isolates, 33% of September isolates, and 100% of the honey isolates did. The predominant honey stomach isolates were Pseudomonas spp. (April), Paenibacillus polymyxa (July, Sept.), and Lonsdalea iberica (Sept.). Chemical characterizations of the antimicrobial compounds show most to be antibiotic in nature with the minority being potential bacteriocins. This study offers the first glimpse into the variability and diversity of the bacteria/host interactions found within the honey stomach of the domestic honey bee while revealing a novel source of potentially beneficial antimicrobial compounds

HONEY MICROBIOME AND METABOLOME: A VAST RESERVOIR OF NATURAL ANTIMICROBIALS

208 pagesRaw honeys contain diverse microbial communities, which have the potential to produce antimicrobial secondary metabolites. These naturally occurring antimicrobials are highly valuable for industry application. Investigating honey microbiome and metabolome can provide important information on factors influencing the microbial communities and antimicrobials produced. In our study, amplicon metagenomics was used to analyze the composition of microorganisms in raw honey and investigate environmental and physicochemical variables that are associated with different microbial communities. The analyzed honey samples had relatively similar bacterial communities but more distinct and diverse fungal communities. Honey type was determined as a significant factor influencing alpha and beta diversity metrics of bacterial and fungal communities. Important bacterial and fungal amplicon sequence variants (ASVs) that influenced the overall community were identified. To obtain novel antimicrobials from natural sources, bacteria from raw honey were isolated and their antifungal-producing potential was evaluated. Naturally occurring antifungal secondary metabolites from these bacteria were further purified and identified. Using mass spectrometry and whole-genome sequence data, the main antifungal compound produced by two Bacillus velezensis isolates was determined as iturin A, a lipopeptide exhibiting broad spectrum antifungal activity. Results from this study provide important insights into the microbial communities associated with different types of raw honey and their antifungal metabolites. This research could improve our understanding of microbial dynamics in beehives, improve honey production, and prevent honeybee disease. Currently, there is a high demand for natural, broad-spectrum, and eco-friendly bio-fungicides in the food industry. Naturally occurring antifungal products from food-isolated bacteria are ideal candidates for agricultural and food applications.2024-09-0

Paenibacillus alvei MP1 as a Producer of the Proteinaceous Compound with Activity against Important Human Pathogens, Including Staphylococcus aureus and Listeria monocytogenes

An emerging need for new classes of antibiotics is, on the one hand, evident as antimicrobial resistance continues to rise. On the other hand, the awareness of the pros and cons of chemically synthesized compounds’ extensive use leads to a search for new metabolites in already known reservoirs. Previous research showed that Paenibacillus strain (P. alvei MP1) recovered from a buckwheat honey sample presented a wide spectrum of antimicrobial activity against both Gram-positive and Gram-negative pathogens. Recent investigation has confirmed that P. alvei MP1 (deposited at DDBJ/ENA/GenBank under the accession WSQB00000000) produces a proteinaceous, heat-stable compound(s) with the maximum antimicrobial production obtained after 18 h of P. alvei MP1 growth in LB medium at 37 °C with continuous shaking at 200 RPM. The highest activity was found in the 40% ammonium sulfate precipitate, with high activity also remaining in the 50% and 60% ammonium sulfate precipitates. Moderate to high antimicrobial activity that is insensitive to proteases or heat treatment, was confirmed against pathogenic bacteria that included L. monocytogenes FSL – X1-0001 (strain 10403S), S. aureus L1 – 0030 and E. coli O157: H7. Further studies, including de novo sequencing of peptides by mass spectrometry, are in progress

Effect of Ethanol Extracts of Propolis (EEPs) against Staphylococcal Biofilm—Microscopic Studies

Staphylococci growing in the form of biofilm exhibit high resistance to a plethora of antibiotics. The aim of the study was to assess the influence of ethanolic extract of propolis (EEPs) on S. epidermidis ATCC 35984 biofilm using fluorescent microscopy. Propidium iodide (PI) and SYTO 9 were used for differentiation of live and dead cells, and calcofluor white was used to stain the extracellular matrix, the self-produced extracellular polymeric substances (EPS). The outcomes of the research confirm the promising potential of EEPs for eradication of staphylococcal biofilm. However, its activity cannot be classified as fully satisfactory, either in terms of the effectiveness of elimination of bacterial cells or disturbing the EPS structure. A two or even four times higher concentration of EEPs compared to MIC (Minimum Inhibitory Concentration) against planktonic cells (128 µg/mL) was necessary for effective (estimated for 90%) elimination of living cells from the biofilm structure. Unfortunately, even at that concentration of EEPs, the extracellular matrix was only partially disturbed and effectively protected the residual population of living cells of S. epidermidis ATCC 35984. In our opinion, a combination of EEPs with agents disrupting components of EPS, e.g., proteases, lysines, or enzymes degrading extracellular DNA or PIA (polysaccharide intercellular adhesin)

Back-sweetened Wine and Apple Cider Inhibit Foodborne Pathogens

In back-sweetened wine and apple cider, lower pH, higher alcohol reduce the risk of pathogens. Extending holding times can help ensure consumer safety in back-sweetened alcoholic beverages.This study was supported by the U.S. Department of Agriculture, National Institute of Food and Agriculture multistate project S-1077, and the College of Agriculture and Life Sciences at Cornell University