Aims The probiotic Bacillus amyloliquefaciens H57 increased weight gain, increased nitrogen retention and increased feed intake in ruminants when administered to the diet. This study aims to develop a better understanding of this probiotic effect by analysing changes in the rumen prokaryotic community. Methods and Results Sequencing the 16S rRNA gene PCR amplicons of the rumen microbiome, revealed that ewes fed H57 had a significantly different rumen microbial community structure to Control sheep. In contrast, dairy calves showed no significant differences in rumen community structure between treatment groups. In both instances, H57 was below detection in the rumen community profile and was only present at low relative abundance as determined by qPCR. Conclusions The altered rumen microbial community in sheep likely contributes to increased weight gain through more efficient digestion of plant material. As no change occurred in the rumen community of dairy calves it is suggested that increased weight gain may be due to changes in community function rather than structure. The low relative abundance of H57 as determined by qPCR, suggests that weight gain was not directly mediated by the probiotic, but rather by influencing animal behaviour (feed consumption) and/or altering the native rumen community structure or function. Significance and Impact of the Study This study provides a novel look at the rumen prokaryotic community in both sheep and dairy calves when fed H57. These findings improve our understanding for the potential rumen community involvement in H57-enabled weight gain. The study reveals that the probiotic B. amyloliquefaciens H57 is capable of benefiting ruminants without colonizing the rumen, suggesting an indirect mechanism of action.

Show that tomato leaf phyllosphere bacteria are candidates for biocontrol of tomato leaf diseases. Seven bacterial isolates from surface sterilized, Moneymaker tomato plants were tested for growth inhibition of 14 tomato pathogens on PDA. Biocontrol assays were conducted with tomato leaf pathogens, Pseudomonas syringae pv. tomato (Pto) and Alternaria solani (A. solani). Two potential isolates showing the greatest inhibition were identified by 16s rDNA sequencing as Rhizobium sp. (isolate b1) and Bacillus subtilis (isolate b2), both produce protease and isolate b2 cellulase. Both reduced tomato leaf infections by Pto and A. solani in detached leaf bioassays. Both bacteria b1 and b2 reduced pathogen development in a tomato growth trial. Bacteria b2 also induced the tomato plant salicylic acid (SA) immune response pathway. Disease suppression in biocontrol assays with b1 and b2 varied between 5 commercial tomato varieties. Tomato phyllosphere bacteria when used as phyllosphere inoculants, inhibited tomato diseases caused by Pto and A. solani.

Sub-therapeutic use of antibiotics as a growth promoter in animal diets has either been banned or voluntarily withdrawn from use in many countries to help curb the emergence of antibiotic-resistant pathogens. Probiotics may be an alternative to antibiotics as a growth promoter. We investigated the effects of a novel probiotic strain Bacillus amyloliquefaciens H57 (H57) on the performance and microbiome-associated metabolic potential. Broiler chickens were fed either sorghum- or wheat-based diets supplemented with the probiotic H57. The growth rate, feed intake and feed conversion in supplemented birds were compared with those in non-supplemented control. Caecal microbial metabolic functions were studied with shotgun metagenomic sequencing. H57 supplementation significantly increased the growth rate and daily feed intake of meat chickens relative to the non-supplemented controls without any effect on feed conversion ratio. In addition, relative to the non-supplemented controls, gene-centric metagenomics revealed that H57 significantly altered the functional capacity of the caecal microbiome, with amino acid and vitamin synthesis pathways being positively associated with H57 supplementation. Bacillus amyloliquefaciens H57 improves the performance of meat chickens or broilers and significantly modifies the functional potential of their caecal microbiomes, with enhanced potential capacity for amino acid and vitamin biosynthesis. A feed supplement like H57, with the ability to enhance weight gain through modulation of intestinal microbial functions, has the potential to be an alternative to antibiotic growth promoters and provide substantial benefits to the poultry industry.