Isolation and identification of bacteria from air coolers in Mosul city, Iraq and study its ability for calcite formation

Evaporative coolers (ECs) are devices used to cool air. They are considered energy-saving and eco-friendly technologies, but eventually precipitate calcite. The present study aimed to isolate calcite-producing bacteria from environmental samples (ECs) and then investigate the influence of environmental parameters, such as pH and temperature, on calcite production. Twenty samples were obtained from sediments on the (ECs) in Mosul city, Iraq. The samples were inoculated on tryptic soy agar. Eleven bacterial isolates were obtained. One of the bacterial isolates exhibited a bush-like growth (complex colony) on tryptic soy agar and was identified using traditional methods. The diagnosis was confirmed by 16S rRNA gene sequencing to be Paenibacillus dendritiformis. The ability of the isolate to synthesize calcite was examined by cultivating it on Luria Bertani acetate agar. The effect of environmental parameters on calcite production was studied by culturing the isolate in Luria-Bertani acetate broth at pH 8, 9, and temperatures of 20°C and 30°C. The strain P. denditiformis demonstrated the capacity to produce calcite crystals in higher rate at pH 8 and 30ºC. Paenibacillus dendritiformis strain NFH1 was submitted to the National Center for Biotechnology Information (NCBI) Gene Bank database, and was shown to be the first strain isolated from air coolers in Iraq.