Brochothrix

Abstract

Bro.cho.thr' ix. Gr. n. brochos a loop; Gr. n. thrix a thread ; N.L. fem. n. Brochothrix loop(ed) thread. Firmicutes / “Bacilli” / Bacillales / “Listeriaceae” / Brochothrix Regular unbranched rods , usually 0.6–0.75 µm in diameter and 1–2 µm in length. Occur singly, in short chains, or in long filament‐like chains that fold into knotted masses . In older cultures the rods may give rise to coccoid forms, which develop into rod forms when subcultured onto a suitable medium. Capsules are not formed. Gram‐positive , but some cells (both rod and coccoid forms) lose the ability to retain the Gram stain. No endospores are produced. Nonmotile. Aerobic and facultatively anaerobic . After 24–48 h, colonies on nutrient agar are opaque, 0.75–1.00 mm in diameter, and convex with entire margin. In older cultures (>2 d) the edge of the colony often breaks up and the center may become raised to give a “fried‐egg” appearance. Nonpigmented . Nonhemolytic. Optimum temperature 20–25°C; growth occurs within the range 0–30°C; over 30°C growth rarely occurs. Catalase is produced. Fermentative metabolism of glucose results in the production of L (+)‐ lactic acid and some other products. Methyl‐red‐positive . Nitrate is not reduced. Indole‐negative. H 2 S‐negative. No growth at pH 3.9 or on acetate medium. Arginine not hydrolyzed. Acid but no gas is produced from a number of carbohydrates. Acetoin and acetate are the major end products of aerobic metabolism of glucose. Usually Voges–Proskauer‐positive. Exogenous citrate and urea not utilized. Enzymes of the tricarboxylic acid cycle are almost totally absent . Organic growth factors are required. The cell wall contains a directly cross‐linked peptidoglycan based upon meso ‐diaminopimelic acid ( meso ‐DAP). Mycolic acids are not present. The long chain fatty acid composition is predominately of the straight chain saturated, iso‐ and anteiso‐methyl‐branched chain types. Menaquinones are the sole respiratory quinones. DNA G + C content ( mol %): 36–38 ( T m ). Type species : Brochothrix thermosphacta (McLean and Sulzbacher 1953) Sneath and Jones 1976, 103 AL ( Microbacterium thermosphactum McLean and Sulzbacher 1953, 432.).