Quorum sensing is known to play a major role in the regulation of secondary metabolite production, especially, antibiotics, and morphogenesis in the phylum Actinobacteria. Although it is one of the largest bacterial phylum, only 25 of the 342 genera have been reported to use quorum sensing. Of these, only nine have accompanying experimental evidence; the rest are only known through bioinformatic analysis of gene/genome sequences. It is evident that this important communication mechanism is not extensively explored in Actinobacteria. In this review, we summarize the different quorum sensing systems while identifying the limitations of the existing screening strategies and addressing the improvements that have taken place in this field in recent years. The γ-butyrolactone system turned out to be almost exclusively limited to this phylum. In addition, methylenomycin furans, AI-2 and other putative AHL-like signaling molecules are also reported in Actinobacteria. The lack of existing screening systems in detecting minute quantities and of a wider range of signaling molecules was a major reason behind the limited information available on quorum sensing in this phylum. However, recent improvements in screening strategies hold a promising future and are likely to increase the discovery of new signaling molecules. Further, the quorum quenching ability in many Actinobacteria has a great potential in controlling the spread of plant and animal pathogens. A systematic and coordinated effort is required to screen and exploit the enormous potential that quorum sensing in the phylum Actinobacteria has to offer for human benefit.

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Two pinkish-red, Gram-stain-negative, non-motile aerobic bacterial strains (MCC P1 T and MCC P2), capable of growing at low temperatures (15 6C), were isolated from water of a saline lake located in the western Himalayas of India. The strains were capable of growth in the presence of 0-2.0 % NaCl and at pH 6.5-9.0. Phylogenetic analysis based on 16S rRNA gene sequences revealed the closest similarity of 96.3 % to the type strain of the only species of the genus Rufibacter, Rufibacter tibetensis CCTCC AB 208084 T . Strains MCC P1 T and MCC P2 shared 99.0 % 16S rRNA gene sequence similarity and 88.6 % DNA-DNA relatedness. The major cellular fatty acids were iso-C 15 : 0 , C 17 : 1 v6c, summed feature 3 (C 16 : 1 v6c/C 16 : 1 v7c) and summed feature 4 (anteiso-C 17 : 1 B/iso-C 17 : 1 I). Predominant polar lipids were phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol. The respiratory quinone was MK-7. The DNA G+C content of the strains was 52.6-52.8 mol%. Based on morphological, physiological, chemotaxonomical and molecular characteristics, strains MCC P1 T and MCC P2 represent a novel species of the genus Rufibacter, for which the name Rufibacter immobilis sp. nov. is proposed. The type strain is MCC P1 T (5MCC 2268 T 5CCTCC AB 2013351 T ).Isolates MCC P1 T and MCC P2 were obtained during microbial diversity studies of one of the least explored high-altitude (4350 m) habitats, Pangong Lake, which extends from the Indian Himalayas to Tibet in China. The isolated strains were pinkish-red and belong to the genus Rufibacter (Abaydulla et al., 2012) based on 16S rRNA gene sequence analysis. The genus Rufibacter was distinguished from other genera of the family Cytophagaceae based on molecular, phylogenetic and phenotypic characters. At the time of writing, Rufibacter tibetensis CCTCC AB 208084 T is the only species of the genus Rufibacter with a validly published name. The novelty of the two isolated strains of the genus Rufibacter was confirmed in a taxonomic study using a polyphasic approach.Since the bacterial count appeared low in the collected samples, a 200 ml water sample was directly spread on agar plates of different nutrient media and grown under varied culture conditions (15-30 u C, pH 7-9, salinity 1-3 %) to correlate the parameters of the sampling habitat. Wellisolated colonies MCC P1 T and MCC P2 from Luria agar (M575; HiMedia) were further transferred onto agar stabs.Cultures were preserved as glycerol stocks and freeze-dried cell mass. Cell morphology was observed by phase-contrast microscopy (BX53; Olympus) and transmission electron microscopy (model TECNAI G2 20; FEI). Gram staining was performed by using a Gram staining kit (K001; HiMedia). Motility was tested by the hanging drop method and observed under a phase-contrast microscope (Suzuki et al., 2001), and confirmation was achieved using the molten agar test (Cruickshank, 1965). Since strains were pigmented, whole-cell absorption spectra were recorded using a Cary 300 UV-Vis spectrophotometer (Agilent Technologies). Anaerobi...

Two Gram-stain-negative, aerobic, alkaliphilic bacteria (strains MEB087T and MEB142) were isolated from sediment and water samples, respectively, collected from the alkaline Lonar Lake in Maharashtra, India. Strains MEB087 T and MEB142 shared 99.8 % 16S rRNA gene sequence similarity and were 85 % related on the basis of DNA-DNA hybridization. et al., 2005) and family Oceanospirillaceae belongs to the class Gammaproteobacteria. It accommodates Gram-stain-negative, non-pigmented, motile, rod-shaped bacteria. At present, the genus Nitrincola comprises one recognized species, Nitrincola lacisaponensis (Dimitriu et al., 2005), isolated from decomposing wood from the shore of a saline, alkaline lake in Grant County, WA, USA. Members of the genus Nitrincola are alkaliphilic, halotolerant, heterotrophic, chemo-organotrophic, and oxidase-and catalase-positive. NO 2 and O 2 can be used as electron acceptors and these bacteria do not grow on fermentable carbon sources. They require sodium for growth. The genus is differentiated from other related genera, Neptunomonas, Marinobacterium and Oceanospirillum, mainly by morphological and physiological characteristics like growth in alkaline conditions and the ability to grow in the absence of NaCl. In this study, we propose a novel species based on two strains (MEB087 T and MEB142) isolated from sediment and water samples collected from Lonar Lake, an alkaline saline lake (pH 9.8) situated in Buldhana district of Maharashtra state, India.Six sediment and water samples were collected in sterile containers from the alkaline Lonar lake at a depth of 0.46 m (1.5 feet) in October 2010 and brought to the laboratory at 4 8C. The temperature and pH of the lake at the time of sampling were 28 8C and pH 9.8, respectively. While strain MEB087T was isolated from a sediment sample, strain MEB142 was isolated from a water sample. For isolating strain MEB087T , 1 g of sediment sample was inoculated in 99 ml of sterile Lonar lake water.