A new beta-1,3-1,4-glucanase gene (PlicA) was cloned from Paenibacillus sp. S09. The ORF contained 717 bp coding for a 238 amino acid protein. PlicA, expressed in Escherichia coli and purified by Ni2+-affinity chromatography, had optimum activity at 55 A degrees C and pH 6.2. The specific activity toward barley beta-glucan reached 7,055 U/mg. K (m) and V (max) values with barley beta-glucan were 3.7 mg/ml and 3.3 x 10(3) mu mol/min mg, respectively. The enzyme exhibited acid- and alkali-tolerance with more than 80 % activity remaining after incubation for 4 h at pH 3.5-12. PlicA was salt-tolerant (> 90 % activity retained in 4 M NaCl at 25 A degrees C for 24 h) and salt-activated: activity rising 1.5-fold in 0.5 M NaCl. The thermostability was improved by NaCl and CaCl2. This is the first report of an acid-, alkali- and salt-tolerant bacterial beta-1,3-1,4-glucanase with high catalytic efficiency.