Xumiao Chen

Characteristics of Rhizobium tianshanense sp. nov., a Moderately and Slowly Growing Root Nodule Bacterium Isolated from an Arid Saline Environment in Xinjiang, People's Republic of China

We performed a numerical analysis of 148 phenotypic characteristics of 20 strains of root nodule bacteria isolated from an arid saline desert soil in the Xinjiang region of northwestern Peoples Republic of China and compared these organisms with 28 Rhizobium and Bradyrhizobium strains obtained from different regions of the Peoples Republic of China and from other countries, including nine type strains of different species. All of the strains examined clustered into two groups at a similarity level of more than 63%. Group I included all of the previously described Rhizobium species and was divided into eight subgroups, which corresponded to previously described Rhizobium species, at a similarity level of more than 82%. Group II was divided into the following three subgroups at a similarity level of more than 80% Bradyrhizobium japonicum, a cluster containing 17 moderately and slowly growing strains isolated in the Xinjiang region, and a small subgroup containing three fast-growing strains. The generation times of the moderately and slowly growing strains were 5 to 15 h, and these organisms produced acid in medium containing mannitol. The DNA G+C contents of the members of this group ranged from 59 to 63 mol%. DNA-DNA hybridization experiments revealed that the levels of DNA homology among all of the moderately and slowly growing strains obtained from Xinjiang were more than 70% and that the levels of DNA homology between representative strains of this group and the type strains of all previously described species of root- and stem-nodulating bacteria were low.(ABSTRACT TRUNCATED AT 250 WORDS)

Morphology and morphogenesis of Apoholosticha sinica n. g., n. sp. (Ciliophora, Hypotrichia), with consideration of its systematic position among urostylids

This paper investigates the morphology, morphogenesis and SSU rRNA gene-based phylogeny of Apoholosticha sinica n. g., n. sp., isolated from mangrove wetland in Shenzhen, southern China. The new genus Apoholosticha is characterized by its bipartite adoral zone, clearly differentiated frontal cirri arranged in a bicorona, midventral complex composed of midventral pairs only, one marginal cirral row on each side, presence of frontoterminal and transverse cirri, and the lack of a buccal cirrus and caudal cirri. The type species, Apoholosticha sinica n. sp. is diagnosed by the elongated body shape and two kinds of cortical granules. Its main morphogenetic features are similar to that of Pseudokeronopsis except for (1) no buccal cirrus is formed and (2) its macronuclear nodules fuse into a single mass during cell division. Phylogenetic analyses for the new taxon indicate that Apoholosticha n. g. is most closely related to Nothoholosticha and Heterokeronopsis, and falls into the family Pseudokeronopsidae within the core Urostylida clade. In addition, a species that had been misidentified in previous literature is here recognized and assigned to the new genus as Apoholosticha sepetibensis (Wanick and Silva-Neto, 2004) n. comb. (basionym: Pseudokeronopsis sepetibensis Wanick and Silva-Neto, 2004).

Phylogeny and systematic revision of the family Pseudokeronopsidae (Protista, Ciliophora, Hypotricha), with description of a new estuarine species of Pseudokeronopsis

Chen, X., Clamp, J. C. & Song, W. (2011). Phylogeny and systematic revision of the family Pseudokeronopsidae (Protista, Ciliophora, Hypotricha), with description of a new estuarine species of Pseudokeronopsis. —Zoologica Scripta, 40, 659–671.

Morphology, morphogenesis and gene sequence of a freshwater ciliate, Pseudourostyla cristata (Ciliophora, Urostyloidea) from the ancient Lake Biwa, Japan.

The urostyloid freshwater ciliate Pseudourostyla cristata was recorded for the first time from Lake Biwa, a 4-million-year-old lake located in Shiga Prefecture, Japan. Its morphology and morphogenesis were investigated using live observation and protargol impregnation, and the SSU ribosomal RNA gene was sequenced. Based on the current observations and previous descriptions, this species is readily recognized mainly by the following characters: body slender or broadly oval to elliptical, and dark grey in color; size in vivo about 170-400 x 40-150 microm; pellicle flexible and contractile, with extrusomes forming a hyaline seam underneath; ciliature comprising about 60-130 adoral membranelles, usually 1 buccal cirrus, 20-24 frontal, 2 frontoterminal, 17-26 pairs of midventral, and 5-16 transverse cirri, 4-6 left and 4-5 right marginal rows, and 8-10 dorsal kineties; 15-83 macronuclear nodules and 2-9 micronuclei; freshwater habitat. The main morphogenetic developments are: (1) the oral primordium for the proter originates de novo on the dorsal wall of the buccal cavity, and the dedifferentiated undulating membranes and some parental proximal membranelles join in the primordial development; the old adoral zone will be partly replaced by new structures; (2) the oral primordium for the opisthe occurs epiapokinetally left of the midventral complex between the adoral zone and the transverse cirri; (3) the fronto-midventral transverse cirral (FVT) anlagen develop separately in both dividers by dedifferentiation of most of the midventral cirri; (4) the single buccal cirrus is generated from the posterior end of FVT anlage II; (5) the leftmost frontal cirrus is derived from the anterior end of the undulating membranes anlage (FVT anlage I); (6) the marginal rows of each side are formed from a single anlage which arises within the rightmost row; (7) the dorsal kineties develop by intrakinetal basal body proliferation; and (8) the most posterior FVT anlage contributes the two fronto-terminal cirri at its anterior end. The present observations indicate that P. cristata has a wide geographic distribution, and possesses constant morphological and morphogenetic traits. Phylogenetic trees inferred from SSU rRNA gene sequences suggest paraphyly of the genus Pseudourostyla.

Evolution of discocephalid ciliates: Molecular, morphological and ontogenetic data support a sister group of discocephalids and pseudoamphisiellids (Protozoa, Ciliophora) with establishment of a new suborder Pseudoamphisiellina subord. n.

Discocephalids and pseudoamphisiellids are possibly two of the most confused groups among hypotrichous/euplotid ciliates regarding their systematic position and phylogenetic relationships. The former were often regarded as related to euplotids while the latter, in the absence of molecular data, were mostly assigned to the urostylid-like hypotrichs. In the present work, the small subunit rRNA genes of several rarely observed discocephalid and pseudoamphisiellid genera were analyzed to obtain insights into the phylogenetic relationships of these highly ambiguous Spirotrichea. Four different tree reconstruction algorithms yielded nearly identical topologies, which indicated both groups belong to the same assemblage. This assemblage is clearly isolated as a deep-branching clade and invariably positioned between Euplotida and Hypotricha. The sister group relationship of the Pseudoamphisiellidae and Discocephalidae supports the previous suggestion that they might represent an ordinal taxon, the Discocephalida. Both morphological and morphogenetic features indicate that the pseudoamphisiellids should be placed in the order Discocephalida but as a sister group to other typical discocephalids. Thus we propose establishing a new suborder, Pseudoamphisiellina subord. n. The new taxon is diagnosed by the following characteristics: (i) two distantly separated midventral rows that are morphogenetically formed with an urostylid mode; (ii) absence of the “frontoterminal row”, which is formed from the posterior-most frontoventral-transverse cirral anlage in all other typical urostylids; (iii) numerous caudal cirri that derive from each of the dorsal kinety anlagen; (iv) right marginal row that has a unique de novo origin; and (v) inhabiting periphytic communities. The validity of the suborder Pseudoamphisiellina is firmly supported by molecular data.

Morphology, ontogeny and molecular phylogeny of a new brackish water ciliate Bakuella subtropica sp. n. (Ciliophora, Hypotricha) from southern China

This paper investigates the morphology, ontogenesis and small subunit (SSU) rRNA gene-based phylogeny of a new urostylid ciliate, Bakuella subtropica sp. n., discovered from the estuary of the Pearl River in Guangzhou, southern China. The new species is diagnosed by its elongate body, one buccal and one parabuccal cirrus, midventral complex comprised of 9-23 midventral pairs and one or two midventral rows extending to four fifths of body length, yellow-brown to yellow-greenish cortical granules and an estuary habitat. Its main ontogenetic features are: (1) in the proter, the parental adoral zone of membranelles is completely renewed by new structures and old midventral pairs join the formation of frontal-midventral-transverse cirral anlagen (FVT-anlagen); (2) in the opisthe, the oral primordium originates apokinetally, FVT-anlagen are formed besides and some old midventral cirri join the formation; (3) the anlagen for marginal rows and dorsal kineties develop intrakinetally; and (4) the numerous macronuclear nodules fuse into a single mass before dividing. Based on the SSU rDNA sequences, phylogenetic analyses show a close relationship between Bakuella subtropica sp. n., Apobakuella and Neobakuella, forming a clade separated from the other genera in the family Bakuellidae. Available morphological and ontogenetic data challenge the monophyly of Bakuellidae.

Morphology and Infraciliature of Two New Marine Urostylid Ciliates : Metaurostylopsis struederkypkeae n. sp. and Thigmokeronopsis stoecki n. sp. (Ciliophora, Hypotrichida) from China

ABSTRACT. The morphology and infraciliature of two new marine urostylid ciliates, Metaurostylopsis struederkypkeae n. sp. and Thigmokeronopsis stoecki n. sp., collected from the coastal waters off Qingdao (Tsingtao), China, have been investigated. Metaurostylopsis struederkypkeae n. sp. is characterized by the slender body shape, small size, rose‐reddish cell colour, and having two kinds of pigment‐like granules. The larger pigment‐like granules are yellow–green or grass‐green in colour, oval in shape, and flattened, whereas the smaller ones are wine‐reddish. Infraciliature and nuclear apparatus are similar to the well‐known Metaurostylopsis marina. Thigmokeronopsis stoecki n. sp. is characterized by its large size with dark brown cell colour and grass‐green cortical granules, which are large, blood‐cell shaped, and sparsely distributed. The thigmotactic ciliature is conspicuous: 11–14 rows of densely arranged cirri occupy the most postoral area. Keys are provided for all the known species in both genera.

Morphology and morphogenesis of a soil ciliate, Rigidohymena candens (Kahl, 1932) Berger, 2011 (Ciliophora, Hypotricha, Oxytrichidae), with notes on its molecular phylogeny based on small-subunit rDNA sequence data.

The morphology and morphogenesis of the stylonychine hypotrich Rigidohymena candens (Kahl, 1932) Berger, 2011, isolated from garden soil in Qingdao, China, were investigated using live observation and protargol impregnation methods. The Qingdao isolate possesses all diagnostic morphological characters of R. candens. The main events during binary fission are as follows: (i) the proter retains the parental adoral zone of membranelles entirely, whereas the old undulating membranes dedifferentiate into an anlage that gives rise to the leftmost frontal cirrus and the new undulating membranes of the proter; (ii) five streaks of fronto-ventral-transverse cirral anlagen are segmented in the pattern 3 : 3 : 3 : 4 : 4 from left to right, which form two frontal, four frontoventral, one buccal, five ventral and five transverse cirri, respectively; (iii) dorsal morphogenesis is in the typical Oxytricha pattern; (iv) three caudal cirri are formed, one at the posterior end of each of dorsal kineties 1, 2 and 4; and (v) the postoral ventral cirrus V/3 is not involved in primordia formation. The morphological and morphogenetic observations and phylogenetic analyses based on the small-subunit rDNA sequence data support the validity of Rigidohymena Berger, 2011 and its systematic position in the subfamily Stylonychinae.

Morphology and molecular phylogeny of two new brackish-water species of Amphisiella (Ciliophora, Hypotrichia), with notes on morphogenesis.

Two new species of the taxonomically confused genus Amphisiella were isolated from brackish-water habitats in southern China, and their morphology and morphogenesis were investigated. The genes coding for small subunit (SSU) rRNA were sequenced in each species and included in a phylogenetic analysis with all data available from nominal species of Amphisiella and related hypotrichs. Both new species are diagnosed by an elongate body shape, yellow-brown/grey-brown cell color, one kind of cortical granule, and two macronuclear nodules. The cortical granules in A. pulchra sp. n. are grouped in small clusters which are irregularly distributed both ventrally and dorsally; in A. candida sp. n., they are irregularly and sparsely distributed ventrally and form longitudinal stripes dorsally. The ontogenetic processes of both species show similarities to those of other congeners. Phylogenetic trees based on SSU rRNA gene sequences suggest that the family Amphisiellidae is a paraphyletic assemblage. The results further demonstrate that two isolates identified as Amphisiella annulata (DQ832260 and GU170843) are very likely cryptic species, and a sequence identified as A. milnei (DQ845293) may belong to a genus other than Amphisiella.

Morphology, morphogenesis and small-subunit rRNA gene sequence of the novel brackish-water ciliate Strongylidium orientale sp. nov. (Ciliophora, Hypotrichia)

A novel stichotrich ciliate, Strongylidium orientale sp. nov., was discovered from a mangrove river in Hong Kong, southern China, and its morphology was investigated through observations in vivo and after protargol impregnation. Cells are 80-120 × 35-50 µm in vivo and fusiform in shape, with rounded anterior and tapered posterior ends. It is characterized by its brackish habitat and by the presence of two types of cortical granules arranged irregularly throughout the cortex. Morphogenetic events of cell division and physiological reorganization are described. The main ontogenetic features were: (i) only the posterior portion of the parental adoral zone of membranelles was renewed by dedifferentiation of the old structures; (ii) the oral primordium in the opisthe occurred apokinetally; (iii) the left and right ventral rows originated intrakinetally and the final left ventral row was spliced from two cirri from the frontoventral cirral anlage, a short cirral row from the anlage for the right ventral row and a long cirral row which was formed from the whole anlage of the left ventral row; (iv) the marginal rows developed intrakinetally; (v) the dorsal kineties replicated entirely de novo and did not fragment; and (vi) the two macronuclear nodules fused into a mass and then divided. Based on small-subunit rRNA gene sequences, phylogenetic analyses showed a close relationship with its congener Strongylidium pseudocrassum and with the genus Pseudouroleptus.