Global Advanced Research Journal of Microbiology (ISSN: 2315-5116) Vol. 1(8) pp. 136-140, September, 2012 Available online http://garj.org/garjm/index.htm Copyright © 2012 Global Advanced Research Journals Full Length Research Paper In vitro, controlling the establishment of Xanthomonas campestris with different bacterial bio-agents Amna Ali* 1 , M. Saleem Haider 2 , Sobia Mushtaq 1 , Ibatsam Khokhar 1 , Irum Mukhtar 1 , Sana Hanif 2 and Nosheen Akhtar 2 1 First Fungal Culture Bank of Pakistan (FCBP), Institute of Agriculture Sciences (IAGS), University of the Punjab, Lahore, 54590, Pakistan. 2 Institute of Agriculture Sciences (IAGS), University of the Punjab, Lahore, 54590, Pakistan Accepted 18 July, 2012 The antimicrobial agents of bacteria isolated from different rhizosphere of fruits and vegetables soil in Lahore. Of ten species, five were gram-negative (Escherichia coli, Pseudomonas fluorescence, Klebsiella pneumoniae, Salmonella typhii, Brachybacterium faecium); other five were gram positive and identified as Bacillus farraginis, Kurthia gibsonii, Aureobacterium liquefaciens, Curtobacterium albidum, Micrococcus lylae. The antagonistic potential of bacterial strains was assessed by the well diffusion technique and results indicating varying degree of biocontrol activity against pathogenic strain of X. campestris. Out of ten bacterial species, E. coli (gram negative) and C. albidum (gram positive) showed a high prevalence of resistance with reduction of 4.2cm and 4.1cm zone diameter respectively. The minimum inhibitory volume (MIV) to two bio-agents was determined for X. campestris from range 10-100 μL. E. coli (volume required to inhibit < 20 μL) and C. albidum (volume required to inhibit < 40 μL) exhibited good activity against pathogen. These results provide information on the prevalence of resistant bacterial strains with the MIV of organisms and indicate the possibility of using these bacterial species as bio-agent against X. campestris. Keywords: Xanthomonas campestris, gram positive bacteria, gram negative bacteria INTRODUCTION The genus Xanthomonas is a diverse and economically essential group of bacterial phytopathogens, belonging to the gamma-subdivision of the Proteobacteria. Xanthomonas campestris is the most important member that causes a variety of plant diseases (Starr and Stephens, 1964). X. campestris causes different diseases in plant foliage by producing black rot, canker, leaf spot and blights. These diseases may destroy leaves, petioles *Corresponding author E-mail: write2amna@gmail.com and stems rendering infected plants unsightly and unsalable (Mariano et al., 2001; Assis et al., 1997). The use of chemical compounds has failed to control plant diseases due to resistance, environment pollution, and damage to human health. Because of these disadvantages, the use of microorganisms for pathogen control and for plant growth promotion is becoming more common (Thomashow and Weller, 1996). However, the success of biocontrol and yield increase depends on the nature of the antagonistic properties and on the mechanisms of action of the organism. The modes of action are widely varied and can be, for instance, nutrient