ISOLATION AND CHARACTERIZATION OF FREE-NITROGEN FIXER BACTERIAL STRAINS (Azotobacter sp.) AND THEIR PHAGES FROM MAIZE RHIZOSPHERE-SOIL AT TAIF

Abstract

We are focusing on isolation of bacteriophage(s) specific to some free N2-fixer bacteria from rhizosphere and
non-rhizosphere soils of Taif region of KSA as a first record for such study in Taif area (Makkah, Jeddah and Taif).
A number of 10 bacterial isolates grown on the nitrogen-free specific medium (Waksman base No.77 Medium) were
purified and separately used as hosts for bacteriophage(s) isolation. The spot test and turbidity tests were used to
detect the presence of the phage of interest in the prepared phage suspensions. The level of lysis revealed the
presence of turbid zones (plaques), as weak (+) lysis (for isolates # 07) and (# 09); moderate lysis (++) (for isolate #
05), and high lysis (+++) (for isolates # 01 and # 03). The phage(s) was propagated and partially purified for
determining the morphology of viral particles via electron microscopy. Sperm shape virus-like particles with long
tail and icosahedral head were shown in the electron micrographs of partially purified phages specific to the two
selected bacterial isolates ((# 01 and # 03). These two bacterial isolates were then morphologically and molecularly
identified. The nucleotide sequences of 16S rRNA gene of the two bacterial isolates was determined and final
sequences of 927 and 873 nts for the 16S rRNA gene of two isolates of this study ((# 01 and # 03), respectively,
were recorded. Data of the phylogentic trees show that the two bacterial isolates (# 01 and # 03) could be strains of
Azotobacter sp. (LC054002.1 and LC054003.1).