The article by R. E. Hungate discusses the isolation and characterization of anaerobic mesophilic cellulolytic bacteria, focusing on nonsporeforming rods and cocci from the bovine rumen. The author emphasizes the importance of pure cultures for studying these bacteria and describes a detailed isolation technique that involves the use of oxygen-free gases, specific culture media, and careful manipulation to minimize air contamination. The isolation technique is crucial for obtaining pure cultures of cellulolytic bacteria, which are often difficult to isolate due to their low abundance and the presence of contaminants. The article highlights the successful isolation of two types of nonsporeforming rods from the rumen: Bacteroides succinogenes, which is highly active in cellulose digestion and produces significant amounts of succinic acid, and a less actively cellulolytic rod that digests cotton or filter paper cellulose incompletely. These bacteria are characterized by their small size, gram-negative reaction, and obligate anaerobic nature. The author also discusses the ecological significance of these bacteria and their role in cellulose decomposition in the rumen. The article concludes with a critical review of the literature on mesophilic sporeformers and provides criteria for determining the purity of cultures, emphasizing the importance of repeated dilution and subculture to ensure the isolation of pure cellulolytic strains.The article by R. E. Hungate discusses the isolation and characterization of anaerobic mesophilic cellulolytic bacteria, focusing on nonsporeforming rods and cocci from the bovine rumen. The author emphasizes the importance of pure cultures for studying these bacteria and describes a detailed isolation technique that involves the use of oxygen-free gases, specific culture media, and careful manipulation to minimize air contamination. The isolation technique is crucial for obtaining pure cultures of cellulolytic bacteria, which are often difficult to isolate due to their low abundance and the presence of contaminants. The article highlights the successful isolation of two types of nonsporeforming rods from the rumen: Bacteroides succinogenes, which is highly active in cellulose digestion and produces significant amounts of succinic acid, and a less actively cellulolytic rod that digests cotton or filter paper cellulose incompletely. These bacteria are characterized by their small size, gram-negative reaction, and obligate anaerobic nature. The author also discusses the ecological significance of these bacteria and their role in cellulose decomposition in the rumen. The article concludes with a critical review of the literature on mesophilic sporeformers and provides criteria for determining the purity of cultures, emphasizing the importance of repeated dilution and subculture to ensure the isolation of pure cellulolytic strains.