Background: Bacterium-bacterium antagonistic interactions could be important in the ecology of marine bacteria. Antimicrobial properties of microorganisms are exploited in various fields of human activities.Objectives: Antagonism of heterotrophic bacteria from different marine environments of tropical and temperate zones was examined.Materials and Methods: Bacteria were isolated from biofilm samples, tissues of hydrobionts and sea water. Isolates were characterized by phenotypic and 16S rRNA phylogenetic analyses. Agar diffusion assay was applied to investigate inhibitory interactions.5 type strains and 21 strains of marine origin were used as test cultures.Results: 68.97% of isolates from temperate zone and 56.76% of tropical zone showed antimicrobial activity. The most active strains belonged to genera Pseudomonas and Pseudoalteromonas.Conclusions: bacterial interspecies growth inhibition is widely distributed in marine environments. Marine bacteria, especially Vibrio spp., may be good probiotics which are active against pathogenic bacteria.

The aim of this study was to evaluate the antimicrobial activities of Trachyspermum ammi, essential oil against different kinds of microorganisms by microtiter plate method. All 36 isolates of (12 Klebsiella pneumoniae, 12 E.coli and 12 Staphylococcus aureus) isolated from urine culture of hospitalized patients (Amir Al-Momenin Hospital, Zabol, south-eastern Iran) suffered from urinary tract infections were evaluated. In this study, the essential oil of Trachyspermum ammi obtained by hydrodistillation for 2.5-3 h using a Clevenger-type apparatus and the minimum inhibitory concentrations were determined to characterize the antimicrobial activities of this essential oil. The results showed E. coli isolates were resistance to 4 of the antibiotics including ceftazidime (50%) cefixime (41.6%), tetracyclin (75%), erythromycin (58.3%). However k. pneumonia isolates were resistance to 3 of the agent including ceftazidime (33.3%), cefixime (58.3%), erythromycin (75%) and S.aureus isolates were resistance to 6 of the agent including cefixime (33.3%), trimethoprim-sulfamethoxazol (41.66%), penicillin (50%), oxacillin (3.3%), ceftazidime (66.6%) and vancomycin (8.3%) and the MIC value was also determined against all the tested bacteria. The highest MIC values of essential oil were determined 100ppm against E.coli and highest MIC value for K.pneumoniae was 250ppm. In conclusion, it seems that Trachyspermum ammi essential oil could inhibit the growth of all of the tested bacteria.