Abstract
Alicyclobacillus acidoterrestris is the main cause of most spoilage problems in fruit juices and acidic products. Since soil borne species often contaminate fruit juices and do not need strict extreme requirements for survival, it is a great concern to investigate whether and how soil species could evolve from their ecological niches in microbial community to new environments as fruit juices. In this study, 23 isolates of thermo-acidophilic, spore-forming bacteria from soil were characterized by cultural and molecular methods. In addition, 2 strains isolated from a spoilage incident in pear juice were typed. Strains phenotyping showed that they could be grouped into 3 different clusters, and some isolates showed identical or quite similar patterns. Analyzing pH and temperature ranges for growth, the majority of strains were able to grow at values described for many species of Alicyclobacillus. Qualitative utilization of lysine, arginine and indole production from tryptophan revealed, for the first time, deamination of lysine and decarboxylation of arginine. Resistance to 5% NaCl as well as the ability to hydrolyze starch and gelatin, nitrate reduction, catalase and oxidase activities confirmed literature evidences. Examining of 16S rRNA, showed that isolates were divided into three blocks represented by effectively soil species and strains that are moving from soil to other possible growing source characterized by parameters that could strongly influence bacterial survival. RAPD PCR technique evidenced a great variability in banding patterns and, although it was not possible to obtain genotypically well-distinguished groups, it was feasible to appreciate genetic similarity between some strains. In conclusion, the investigation of a microbial community entails a combination of metagenomic and classic culture-dependent approaches to expand our knowledge about Alicyclobacillus and to look for new subspecies.
Highlights
In 1987, Deinhard and coworkers proposed that the species of Bacillus mainly isolated from soil and characterized by acid loving behavior would be called acidoterrestris [1]
Strains belong to a private collection of the Department of the Science of Agriculture, Food and Environment (SAFE) (Foggia University). 23 strains were randomly selected from soil of Foggia and named with capital letter C and 2 strains isolated from a spoilage incident in pear juice
In order to understand whether A. acidoterrestris could adapt in different ecological niches, 23 isolates of thermo-acidophilic, spore-forming bacteria taken from ground were characterized by using cultural and molecular (16S rDNA and RAPD) methods
Summary
In 1987, Deinhard and coworkers proposed that the species of Bacillus mainly isolated from soil and characterized by acid loving behavior would be called acidoterrestris [1]. Alicyclobacillus genus grouped Gram positive, thermo-acidophilic, rod-shaped, non-pathogenic and spore-forming microorganisms with unusual ω-alicyclic fatty acids in their cell membrane. They can grow in highly acidic environments (2.5–6.0 pH) and at temperatures of 25–60°C [3,4]. The main characteristic of these species is the ability to spoil juices and acidic products by producing guaiacol and other halophenols [2; 6,7,8]. 23 isolates of thermo-acidophilic, spore-forming bacteria from soil and 2 strains from spoiled pear juice were characterized at biochemical and molecular levels to appreciate genomic and phenotypic differences between environment and juice bacteria
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