Table 1. Effect of DNase I and proteinase K on biofilm formation of Hrr. lacusprofundi.

Treatment	Biofilm biomass		Total intra- and extra-cellular DNA
	Bicinchoninic acid assay (total protein μg)	Crystal violet assay (OD600)	Acridine orange assay [(LAU-B) mm−2]
Control	1400 ± 30	1.0 ± 0.1	101000 ± 1100
DNase I 10 μg mL−1	1100 ± 60*	0.75 ± 0.08**	76000 ± 710**
DNase I 100 μg mL−1	600 ± 40**	0.50 ± 0.05***	26800 ± 270***
Proteinase K 0.1 μg mL−1	1900 ± 50*	1.7 ± 0.1***	181000 ± 9700*
Proteinase K 1 μg mL−1	1500 ± 60	1.1 ± 0.09	257000 ± 12000**
Proteinase K 10 μg mL−1	17 ± 6***	0.03 ± 0.01****	3190 ± 130***

Bicinchoninic acid, crystal violet and acridine orange assays were performed at 10 d. The results are the means ± standard errors from three biological replicates. Asterisks indicate the significance of the difference compared to the value for the control, calculated using a paired t-test: *p < 0.05, **p < 0.01, ***p < 0.001; ****p < 0.0001.