PLANT-BORNE COMPOUNDS AND NANOPARTICLES: CHALLENGES FOR MEDICINE, PARASITOLOGY AND ENTOMOLOGY Brevibacillus laterosporus isolated from the digestive tract of honeybees has high antimicrobial activity and promotes growth and productivity of honeybee’ s colonies Jamal M. Khaled 1,2 & Fahd A. Al-Mekhlafi 3,4 & Ramzi A. Mothana 5 & Naiyf S. Alharbi 1 & Khalid E. Alzaharni 6,7 & Anwar H. Sharafaddin 8 & Shine Kadaikunnan 1 & Ahmed S. Alobaidi 1 & Noofal I. Bayaqoob 8 & Marimuthu Govindarajan 9 & Giovanni Benelli 10,11 Received: 8 June 2017 /Accepted: 1 September 2017 # Springer-Verlag GmbH Germany 2017 Abstract The development of novel antimicrobial drugs, as well as the discovery of novel compounds able to promote honeybee’ s growth, represents major challenges for modern entomology. The main aim of this study was to investigate whether Brevibacillus laterosporus isolated from the digestive tract of Saudi honeybees, Apis mellifera, was able to stimulate colony strength parameters of honeybees and to evaluate its ability to produce antimicrobial agents. Honeybees were col- lected in Dirab, Riyadh Region, Saudi Arabia, and microor- ganisms were isolated and identified by 16S ribosomal RNA analysis. Microscopic identification of the microorganism in its native state was facilitated by atomic force microscopy at high-resolution imaging. Active biological compounds were produced by submerged fermentation with B. laterosporus. The fermented broth was subjected to extraction and purifica- tion, and then semi-pure compounds were analyzed by gas chromatography–mass spectrometry. The effectiveness of the crude extract and semi-pure compounds as antimicrobial agents was evaluated by susceptibility assays. More than 22% of the microorganisms isolated from the digestive tract of healthy honeybees have been identified as B. laterosporus, this kind of species has a unique shape and morphological structure. The cyclic dipeptide cyclo(Leu-Pro) produced by B. laterosporus showed biological activity against several pathogenic microorganisms. Furthermore, the total counts of workers, closed brood, and open brood, as well as the produc- tion of bee pollen and honey, were better in honeybees treated with a B. laterosporus suspension. The data indicated that the Responsible editor: Philippe Garrigues * Jamal M. Khaled gkhaled@ksu.edu.sa * Shine Kadaikunnan sshine@ksu.edu.sa 1 Department of Botany and Microbiology, College of Science, King Saud University, Riyadh 11451, Saudi Arabia 2 Department of Biotechnology and Food Technology, Thamar University, Thamar, Yemen 3 Bioproducts Research, Department of Zoology, College of Science, King Saud University, Riyadh, Saudi Arabia 4 Department of Agricultural Production, College of Agriculture and Veterinary Medicine, Thamar University, Thamar, Yemen 5 Department of Pharmacognosy, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia 6 Department of Physics and Astronomy, King Saud University, Riyadh 11451, Saudi Arabia 7 King Abdullah Institute for Nanotechnology, King Saud University, Riyadh 11451, Saudi Arabia 8 Department of Plant Protection, Faculty of Food and Agriculture Sciences, King Saud University, Riyadh 11451, Saudi Arabia 9 Unit of Vector Control, Phytochemistry and Nanotechnology, Department of Zoology, Annamalai University, Annamalainagar, Chidambaram, Tamil Nadu 608 002, India 10 Department of Agriculture, Food and Environment, University of Pisa, Via del Borghetto 80, 56124 Pisa, Italy 11 The BioRobotics Institute, Scuola Superiore Sant’Anna, Viale Rinaldo Piaggio 34, Pontedera, 56025 Pisa, Italy Environ Sci Pollut Res DOI 10.1007/s11356-017-0071-6