Unusual non-fluorescent broad spectrum siderophore activity (SID EGYII) by Pseudomonas aeruginosa strain EGYII DSM 101801 and a new insight towards simple siderophore bioassay

Amira M. Embaby, Yasmin Heshmat, Ahmed Hussein

Present study highlights an unusual non-fluorescent hydroxamate broad spectrum siderophore (SID EGYII) activity from Pseudomonas aeruginosa strain EGYII DSM 101801, a soil bacterial isolate, along with simple low cost effective siderophore bioassay. Detection of SID EGYII activity qualitatively was proved by masking this activity against Erwinia amylovora strain EGY1 DSM 101800, an indicator strain, in well-cut diffusion assay containing 100 µM FeCl3. SID EGYII activity was expressed quantitatively as arbitrary units [Siderophore arbitrary units (SAU)] 380 SAU/mL against E. amylovora strain EGY1 DSM 101800. Maximal SID EGYII activity was achieved upon growing P. aeruginosa strain EGYII DSM 101801 in PYB broth at 180 rpm for 24 h. SID EGYII displayed a broad spectrum antimicrobial activity against some human pathogens (i.e., Gram-positive bacteria, Gram-negative bacteria and yeasts) and a fireblight plant pathogen. Interestingly, transformants of Escherichia coli JM109 (DE3)pSID/EGYII harboring P. aeruginosa strain EGYII DSM 101801 plasmid demonstrated a perceivable antimicrobial activity against E. amylovora strain EGY1 DSM 101800. The broad spectrum antimicrobial activity of the unusual non-fluorescent SID EGYII would underpin its high potential in targeting bacterial pathogens posing probable threats to human health and agricultural economy. The present simple low cost effective bioassay is a new insight towards an alternative to the expensive cumbersome siderophore Chrome Azurol S assay.