Kocuria rhizophila

Abstract: Rice (Oryza sativa) is a staple food in Thailand and, in addition, feeds around one half of the world’s population. Therefore, diseases of rice are of special concern. Rice is destroyed by 2 main pathogens, Fusarium oxysporum and Pyricularia oryzae the causative agents of root rot and blast in rice respectively. These pathogens result in low grain yield in Thailand and other Southeast Asian countries. Soil samples were taken from paddy fields in Northern Thailand and bacteria were isolated using the soil dilution plate method on Nutrient agar. Isolation yielded 216 bacterial isolates which were subsequently tested for their siderophore production and effectiveness in inhibiting mycelial growth in vitro of the rice pathogenic fungi; Alternaria sp., Fusarium oxysporum, Pyricularia oryzae and Sclerotium sp., the causal agent of leaf spot, root rot, blast and stem rot in rice. It was found that 23% of the bacteria isolated produced siderophore on solid plating medium and liquid medium, In dual culture technique, the siderophore producing rhizobacteria showed a strong antagonistic effect against the Alternaria (35.4%), Fusarium oxysporum (37.5%), Pyricularia oryzae (31.2%) and Sclerotium sp. (10.4%) strains tested. Streptomyces sp. strain A 130 and Pseudomonas sp. strain MW 2.6 in particular showed a significant higher antagonistic effect against Alternaria sp. while Ochrobactrum anthropi D 5.2 exhibited a good antagonistic effect against F. oxysporum. Bacillus firmus D 4.1 inhibited P. oryzae and Kocuria rhizophila 4(2.1.1) strongly inhibited Sclerotium sp. P. aureofaciens AR 1 was the best siderophore producer overall and secreted hydroxamate type siderophore. This strain exhibits an in vitro antagonistic effect against Alternaria sp., F. oxysporum and P. oryzae. Siderophore production in this isolate was maximal after 15 days and at an optimal temperature of 30°C, yielding 99.96 ± 0.46 μg ml−1 of siderophore. The most effective isolates were identified by biochemical tests and molecular techniques as members of the Genus Bacillus, Pseudomonas and Kocuria including B. firmus D 4.1, P. aureofaciens AR1 and Kocuria rhizophila 4(2.1.1). The study demonstrated antagonistic activity towards the target pathogens discussed and are thus potential agents for biocontrol of soil borne diseases of rice in Thailand and other countries.

Abstract: Bacterial biodiversity occurring in traditional Egyptian soft Domiati cheese was studied by PCR-temporal temperature gel electrophoresis (TTGE) and PCR-denaturing gradient gel electrophoresis (DGGE). Bands were identified using a reference species database (J.-C. Ogier et al., Appl. Environ. Microbiol. 70:5628-5643, 2004); de novo bands having nonidentified migration patterns were identified by DNA sequencing. Results reveal a novel bacterial profile and extensive bacterial biodiversity in Domiati cheeses, as reflected by the numerous bands present in TTGE and DGGE patterns. The dominant lactic acid bacteria (LAB) identified were as follows: Leuconostoc mesenteroides, Lactococcus garvieae, Aerococcus viridans, Lactobacillus versmoldensis, Pediococcus inopinatus, and Lactococcus lactis. Frequent non-LAB species included numerous coagulase-negative staphylococci, Vibrio spp., Kocuria rhizophila, Kocuria kristinae, Kocuria halotolerans, Arthrobacter spp./Brachybacterium tyrofermentans. This is the first time that the majority of these species has been identified in Domiati cheese. Nearly all the dominant and frequent bacterial species are salt tolerant, and several correspond to known marine bacteria. As Domiati cheese contains 5.4 to 9.5% NaCl, we suggest that these bacteria are likely to have an important role in the ripening process. This first systematic study of the microbial composition of Domiati cheeses reveals great biodiversity and evokes a role for marine bacteria in determining cheese type.

Abstract: Two Gram-positive, aerobic spherical actinobacteria were isolated from the rhizoplane of narrow-leaved cattail (Typha angustifolia) collected from a floating mat in the Soroksar tributary of the Danube river, Hungary. Sequence comparisons of the 16S rDNA indicated these isolates to be phylogenetic neighbours of members of the genus Kocuria, family Micrococcaceae, in which they represent two novel lineages. The phylogenetic distinctness of the two organisms TA68T and TAGA27T was supported by DNA-DNA similarity values of less than 55% between each other and with the type strains of Kocuria rosea, Kocuria kristinae and Kocuria varians. Chemotaxonomic properties supported the placement of the two isolates in the genus Kocuria. The diagnostic diamino acid of the cell-wall peptidoglycan is lysine, the interpeptide bridge is composed of three alanine residues. Predominant menaquinone was MK-7(H2). The fatty acid pattern represents the straight-chain saturated iso-anteiso type. Main fatty acid was anteiso-C15:0. The phospholipids are diphosphatidylglycerol, phosphatidylglycerol and an unknown component. The DNA base composition of strains TA68T and TAGA27T is 69.4 and 69.6 mol% G+C, respectively. Genotypic, morphological and physiological characteristics are used to describe two new species of Kocuria, for which we propose the names Kocuria palustris, type strain DSM 11925T and Kocuria rhizophila, type strain DSM 11926T.