Abstract The main objective of the present study was to develop and validate a new alternative modelling method to predict Bacillus tequilensis count in nutrient broth under iso-thermal and non-isothermal conditions. The bacterial growth data of Bacillus tequilensis was obtained experimentally in aerobically-kept nutrient broth medium and described with two-step and one-step modelling approaches by different primary models (the modified Gompertz, logistic, Baranyi and Huang models) under isothermal temperatures. Temperature-dependent kinetic parameter (maximum specific growth rate ‘µmax’) was described as a function of temperature via the Ratkowsky model integrated with each primary model. The Huang model based on the one-step modelling approach yielded the best fitting results (RMSE = 0.143 and adjusted-R2 = 0.977) for all isothermal conditions. Therefore, the Huang model was also used to check it’s prediction capability under non-isothermal conditions. The differential form of the Huang model provided satisfactorily statistical indexes (Bf = 1.07 and Af = 1.08) indicating reliably being able to use to describe the growth behaviour of Bacillus tequilensis in broth subjected to non-isothermal conditions.

One of the most economically important bacterial pathogens of plants and plant products is Dickeya dadantii. This bacterium causes soft rot disease in tubers and other parts of the potato and other plants of the Solanaceae family. The application of restricted host range bacteriophages as biocontrol agents has recently gained widespread interest. This study purposed to isolate the infectious agent of the potato and evaluate its biocontrol by bacteriophages. Two phytopathogenic strains were isolated from infected potatoes, identified based on biochemical and 16S rRNA gene sequencing, and submitted to GenBank as D. dadantii strain pis3 (accession no. HQ423668) and D. dadantii strain sip4 (accession no. HQ423669). Their bacteriophages were isolated from Caspian Sea water by enriching the water filtrate with D. dadantii strains as hosts using spot or overlay methods. On the basis of morphotypes, the isolated bacteriophages were identified as members of the Myoviridae and Siphoviridae families and could inhibit the growth of antibiotic resistant D. dadantii strains in culture medium. Moreover, in Dickeya infected plants treated with bacteriophage, no disease progression was detected. No significant difference was seen between phage-treated and control plants. Thus, isolated bacteriophages can be suggested for the biocontrol of plant disease caused by Dickeya strains.