Research Paper Paenibacillus marinum sp. nov., a thermophilic xylanolytic bacterium isolated from a marine hot spring in Tunisia Hanene Bouraoui 1 , Hanen Rebib 2 , Melek Ben Aissa 1 , Jean Pierre Touzel 3 , Michael O’donohue 4, 5 and Mohamed Manai 1 1 Laboratoire de Biochimie et Biologie Moléculaire, Université de Tunis El Manar, Faculté des Sciences de Tunis, Tunis, Tunisie, 2 Laboratoire des Microorganismes et Biomolécules Actives, Université de Tunis El Manar, Faculté des Sciences de Tunis, Tunis, Tunisie, 3 INRA, UMR614 Fractionnement des AgroRessources et Environnement, Reims, France 4 Université de Toulouse, INSA, UPS, INP, LISBP, F-31077, Toulouse, France 5 INRA, UMR792 Ingénierie des Systèmes Biologiques et des Procédés, France Among a large collection of Tunisian hot springs bacterial isolates a bacterial strain, THE22 T , with xylanolytic properties was identified. The bacterium was isolated from a natural hot spring “ Ain Echefa” at Mediteranean sea (Korbous, North-Eastern Tunisia). The novel strain was Gram positive, spore-forming, rod-shaped, facultatively anaerobic and grew optimally under conditions of 55 °C, 1% (w/v) NaCl and pH 7–8. The 16S rRNA gene sequence analysis showed that strain THE22 T fell within the radiation of the cluster comprising Paenibacillus species with Paenibacillus phyllosphaerae PALXIL04 T as the closest phylogenetic neighbour (95.8%). The predominant components in the fatty methyl ester profile were iso-C 16:0 (34.46%), C 16:0 (19.64%), anteiso-C 15:0 (19.18%) and anteiso- C 17:0 (18.11%). The major respiratory quinone was menaquinone-7 (MK-7). The diamino acid found in the cell-wall peptidoglycan was meso-diaminopimelic acid. The base composition of DNA was 56 mol%. Based on the polyphasic taxonomic data, strain THE-22 T (¼DSM 18499 T ¼ LMG 23758 T ) was recognized as a novel species within the genus Paenibacillus. The name Paenibacillus marinum sp. nov. is proposed. : Additional supporting information may be found in the online version of this article at the publisher’s web-site Keywords: Marine hot spring / Thermophile / Paenibacillus marinum / Xylan Received: May 18, 2012; accepted: July 14, 2012 DOI 10.1002/jobm.201200275 Introduction Thermophilic microorganisms have gained much atten- tion for their unique genetic types and physiological mechanism and their metabolic enzymes have good acid and alkali-resistant, heat resistant and harmful substance resistant properties [35]. The use of thermophilic micro- organisms and their robust enzymes for the sustainable production of chemicals, biopolymers, materials, and fuels from renewable resources, defined as industrial biotech- nology, offers many opportunities for various branches of industry [9, 10]. Thermostable enzymes are mostly applied in molecular biology (e.g. DNA polymerases) and in processes requiring hydrolysis of proteic substrates, lipidic substrates, or polysaccharides [22, 36]. The Detergent manufacturing industry, sugar industry, pulp and paper producers as well as industrial textile manufacturers are interested on thermostable proteases, lipases, amylases, cellulases and xylanases [7, 11, 21]. The discovery of thermophilic microorganisms with unique properties can therefore have a great impact in terms of these industrial applications. Thermophiles have been isolated in the past from various environments including oil reservoirs, deep Correspondence: Dr. Hanene Bouraoui, Laboratoire de Biochimie et Biologie Moléculaire, Université de Tunis El Manar, Faculté des Sciences de Tunis, 2092 Tunis, Tunisie E-mail: hanenebouraoui@yahoo.fr Phone: þ216 97519 337 Environment  Health  Techniques Paenibacillus marinum sp. nov., a thermophilic xylanolytic bacterium 877 ß 2013 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim www.jbm-journal.com J. Basic Microbiol. 2013, 53, 877–883