The microbial community of Baikal sponges has been studied in five species belonging to the genera Swartschewskia, Baicalospongia, and Lubomirskia of the endemic family Lubomirskiidae. The results show that the total numbers of bacteria and bacterioplankton production have an effect on the growth of L. baicalensis body. Bacteria of the genera Pseudomonas, Bacillus, Micrococcus, Sarcina, Flavobacterium, Arthrobacter, and Acinetobacter living in the sponges are representatives of the Baikal bacterioplankton. Actinomycetes of the genera Streptomyces and Micromonospora are a permanent component of the cultivable sponge microbial community. The numbers and enzyme activities of heterotrophic, oligotrophic, and psychrophilic bacteria isolated from different sponge species and the surrounding water in autumn and in winter have been estimated.