Emended description of the genus Tabrizicola and the species Tabrizicola aquatica as aerobic anoxygenic phototrophic bacteria

Analyzing the Interaction between Tetrahymena pyriformis and Bacteria under Different Physicochemical Conditions When Infecting Guppy Using the eDNA Method

In the aquaculture system of ornamental fish, the interaction between bacterial microbiota and ciliate protozoa can prevent or promote disease outbreaks, and different physicochemical conditions will affect the relationships between them. We investigated the interaction between bacterial microbiota and the parasite Tetrahymena pyriformis when infecting Poecilia reticulata (guppy) under different physicochemical conditions. The abundance of T. pyriformis in water, the relative abundance of bacterial species, and histopathological observation were studied or monitored using environmental DNA (eDNA) extraction technology, the qPCR method, and 16s rRNA sequencing, respectively. The morphological identification and phylogenetic analysis of T. pyriformis were carried out. The infected guppy tissue was also stained by the hematoxylin and eosin methods. The results showed: (1) the bacterial communities of water samples were mainly composed of species assigned to Proteobacteria and Bacteroidetes, and Tabrizicola and Puniceicoccaceae were positively correlated with fish mortality, T. pyriformis abundance, and temperature. (2) Arcicella and Methyloversatilis universalis with different correlations between ciliates appeared in different treatment groups, the result of which proved that environmental factors affected the interaction between bacteria and T. pyriformis. (3) Lower temperatures and a higher pH were more beneficial for preventing disease outbreaks.

Aquaculture ecosystem microbiome at the water-fish interface: the case-study of rainbow trout fed with Tenebrio molitor novel diets

BACKGROUND

Sustainable aquaculture relies on multiple factors, including water quality, fish diets, and farmed fish. Replacing fishmeal (FM) with alternative protein sources is key for improving sustainability in aquaculture and promoting fish health. Indeed, great research efforts have been made to evaluate novel feed formulations, focusing especially on the effects on the fish gut microbiome. Few studies have explored host-environment interactions. In the present study, we evaluated the influence of novel insect-based (Tenebrio molitor) fish diets on the microbiome at the water-fish interface in an engineered rainbow trout (Oncorhynchus mykiss) farming ecosystem. Using 16S rRNA gene metabarcoding, we comprehensively analyzed the microbiomes of water, tank biofilm, fish intestinal mucus, fish cutis, and feed samples.

RESULTS

Core microbiome analysis revealed the presence of a highly reduced core shared by all sample sources, constituted by Aeromonas spp., in both the control and novel feed test groups. Network analysis showed that samples were clustered based on the sample source, with no significant differences related to the feed formulation tested. Thus, the different diets did not seem to affect the environment (water and tank biofilm) and fish (cutis and intestinal mucus) microbiomes. To disentangle the contribution of feed at a finer scale, we performed a differential abundance analysis and observed differential enrichment/impoverishment in specific taxa, comparing the samples belonging to the control diet group and the insect-based diet group.

CONCLUSIONS

Omic exploration of the water-fish interface exposes patterns that are otherwise undetected. These data demonstrate a link between the environment and fish and show that subtle but significant differences are caused by feed composition. Thus, the research presented here is a step towards positively influencing the aquaculture environment and its microbiome.

Genomic Analysis and Characterization of Pseudotabrizicola formosa sp. nov., a Novel Aerobic Anoxygenic Phototrophic Bacterium, Isolated from Sayram Lake Water

Aerobic anoxygenic photosynthetic bacteria (AAPB) are a kind of heterotrophic prokaryote that can use bacteriochlorophyll (BChl) for photosynthesis without oxygen production and they are widely distributed in aquatic environments, including oceans, lakes, and rivers. A novel aerobic anoxygenic photosynthetic bacterium strain XJSPT was isolated during a study of water microbial diversity in Sayram Lake, Xinjiang Province, China. Strain XJSPT was found to grow optimally at 33 °C, pH 7.5 with 1.0% (w/v) NaCl, and to produce bacteriochlorophyll a and carotenoids. Phylogenetic analysis based on 16S rRNA gene sequence and concatenated alignment sequences of 120 ubiquitous single-copy proteins both supported that strain XJSPT belonged to the genus Pseudotabrizicola. Both average nucleotide identity (ANI) and DNA-DNA hybridization (DDH) values were below the species delineation threshold. The primary polar lipids were phosphatidylcholine, phosphatidylglycerol, phosphatidylethanolamine, one unknown lipid, and one unidentified phospholipid. Based on the results of polyphasic analyses performed in this study, strain XJSPT represents a new member of the genus Pseudotabrizicola, for which the name Pseudotabrizicola formosa sp. nov. is proposed. The type strain is XJSPT (=KCTC 52636T = MCCC 1H00184T = SDUM 107003T). Comparative genomic analysis showed that four species of the genus Pseudotabrizicola shared 2570 core genes and possessed a complete anoxygenic photosystem II.

Tabrizicola rongguiensis sp. nov., isolated from the sediment of a river in Ronggui, Foshan city, China

A novel Gram-negative, aerobic, non-spore-forming, non-motile and rod-shaped bacterium, designated J26^T, was isolated from the sediment of a river in Ronggui, Foshan city, China. Strain J26^T grew optimally at 0 % (w/v) NaCl, pH 6.5-7.5, and 30 °C, and it formed milky white irregular colonies on Reasoner's 2A agar medium. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain J26^T had the highest similarity to Tabrizicola aquatica RCRI19^T (97.1 %) and formed a distinct clade in the genus Tabrizicola. Cellular components of J26^T supported this strain as a member of the genus Tabrizicola. The predominant fatty acids were C_18 : 1  ω7c, C_18 : 1  ω7c-11 methyl and C_16 : 0. Polar lipids were diphosphatidylglycerol, phosphatidylglycerol and phosphorylethanolamine. Ubiquinone Q-10 was the major respiratory quinone, and the DNA G+C content was 64.2 mol%. However, low 16S rRNA gene sequence similarity and average nucleotide identity (73.56 % for ANIb between strain J26^T with RCRI19^T) demonstrated that strain J26^T should be assigned to a novel species. Moreover, the differences between J26^T and RCRI19^T in terms of physiological and biochemical properties, such as carbon, nitrogen and sulphur metabolism, further supported that J26^T represents a novel species, for which the name Tabrizicola rongguiensis sp. nov. is proposed. The type strain is J26^T (=GDMCC 1.2843^T=KCTC 92112^T).

Neotabrizicola shimadae gen. nov., sp. nov., an aerobic anoxygenic phototrophic bacterium harbouring photosynthetic genes in the family Rhodobacteraceae, isolated from a terrestrial hot spring

A bacteriochlorophyll-containing bacterium, designated as strain N10^T, was isolated from a terrestrial hot spring in Nagano Prefecture, Japan. Gram-stain-negative, oxidase- and catalase-positive and ovoid to rod-shaped cells showed the features of aerobic anoxygenic phototrophic bacteria, i.e., strain N10^T synthesised bacteriochlorophylls under aerobic conditions and could not grow anaerobically even under illumination. Genome analysis found genes for bacteriochlorophyll and carotenoid biosynthesis, light-harvesting complexes and type-2 photosynthetic reaction centre in the chromosome. Phylogenetic analyses based on the 16S rRNA gene sequence and 92 core proteins revealed that strain N10^T was located in a distinct lineage near the type species of the genera Tabrizicola and Xinfangfangia and some species in the genus Rhodobacter (e.g., Rhodobacter blasticus). Strain N10^T shared < 97.1% 16S rRNA gene sequence identity with those species in the family Rhodobacteraceae. The digital DNA-DNA hybridisation, average nucleotide identity and average amino acid identity values with the relatives, Tabrizicola aquatica RCRI19^T (an aerobic anoxygenic phototrophic bacterium), Xinfangfangia soli ZQBW^T and R. blasticus ATCC 33485^T were 19.9-20.7%, 78.2-79.1% and 69.1-70.1%, respectively. Based on the phenotypic features, major fatty acid and polar lipid compositions, genome sequence and phylogenetic position, a novel genus and species are proposed for strain N10^T, to be named Neotabrizicola shimadae (= JCM 34381^T = DSM 112087T). Strain N10^T which is phylogenetically located among aerobic anoxygenic phototrophic bacteria (Tabrizicola), bacteriochlorophyll-deficient bacteria (Xinfangfangia) and anaerobic anoxygenic phototrophic bacteria (Rhodobacter) has great potential to promote studies on the evolution of photosynthesis in Rhodobacteraceae.

Antimicrobial activity of Bacillus sp. isolated strains of wild honey

BACKGROUND

Multi-drug resistant bacteria hazards to the health of humans could be an agent in the destruction of human generation. Natural products of Bacillus species are the main source to access progressive antibiotics that can be a good candidate for the discovery of novel antibiotics. Wild honey as a valuable food has been used in medicine with antimicrobial effects.

OBJECTIVE

Bacillus strains isolated from wild honey were evaluated for the potential antimicrobial activity against human and plant bacterial and fungal pathogens.

METHODS

Three bacterial isolates were identified as strain Khuz-1 (98.27% similarity with Bacillus safensis subsp. Safensis strain FO-36bT), strain Khuz-2 (99.18% similarity with Bacillus rugosus strain SPB7T), and strain Khuz-3 (99.78% similarity with Bacillus velezensis strain CR-502 T) by 16S rRNA gene sequences. The strains were characterized by their ability to inhibit the growth of human and phytopathogenic fungi.

RESULTS

The results indicated that B. rugosus strain Khuz-2 inhibited the growth of phytopathogenic and human fungal more effective than other ones. It seems that the strain Khuz-2 has a suitable antimicrobial and antifungal potential as a good candidate for further pharmaceutical research.

CONCLUSION

Based on the results of GC-MS, Pyrrolo [1,2-a] pyrazine-1,4-dion, hexahydro-3-(2-methylpropyle) (PPDHM) was the major compound for all strains which have a various pharmacological effect. Isolation and identification of beneficial bacteria from natural sources can play an important role in future pharmaceutical and industrial applications.

Szabonella alba gen. nov., sp. nov., a motile alkaliphilic bacterium of the family Rhodobacteraceae isolated from a soda lake

A Gram-stain-negative, oxidase- and catalase-positive, rod-shaped, creamy white coloured bacterial strain, DMG-N-6T, was isolated from a water sample of Lake Fertő/Neusiedler See (Hungary). Phylogenetic analysis based on 16S rRNA gene sequences revealed that the strain forms a distinct linage within the family Rhodobacteraceae . Its closest relatives are Tabrizicola alkalilacus DJCT (96.76% similarity) and Tabrizicola piscis K13M18T (96.76%), followed by Tabrizicola sediminis DRYC-M-16T (96.69 %), Rhodobacter sediminicola JA983T (96.62 %), Tabrizicola aquatica RCRI19T (96.47 %) and Cereibacter johrii JA192T (96.18 %). The novel bacterial strain favours an alkaline environment (pH 8.0-12.0) and grows optimally at 18–28°C in the presence of 2–4 % (w/v) NaCl. Cells of DMG-N-6T were motile by a single subpolar flagellum. Bacteriochlorophyll a was not detected. The predominant respiratory quinone was ubiquinone Q-10. The major cellular fatty acid was C18:1 ω7c. The polar lipid profile comprised phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylserine, phosphatidylcholine, an unidentified phospholipid and five unidentified lipids. The assembled draft genome of strain DMG-N-6T had 52 contigs with a total length of 4 219 778 bp and a G+C content of 64.3 mol%. Overall genome-related indices (ANI <77.8 %, AAI <69.0 %, dDDH <19.6 %) with respect to close relatives were all significantly below the corresponding threshold to demarcate bacterial genus and species. Strain DMG-N-6T (=DSM 108208T=NCAIM B.02645T) is strongly different from its closest relatives and is suggested as the type strain of a novel species of a new genus in the family Rhodobacteraceae , for which the name Szabonella alba gen. nov., sp. nov. is proposed.

Seasonal variation significantly affected bacterioplankton and eukaryoplankton community composition in Xijiang River, China

Both bacterioplankton and eukaryoplankton communities play important roles in the geochemical cycles and energy flows of river ecosystems. However, whether a seasonal change in bacterioplankton and eukaryoplankton communities is synchronous remains unclear. To test the synchronicity and analyze how physical and chemical environmental factors affect these communities, we compared bacterioplankton and eukaryoplankton communities in surface water samples between March (dry season) and June (rainfall season) considering water environmental factors. Our results showed that there was no significant difference in operational taxonomic unit number, Shannon index, and Chao1 index in bacterioplankton and eukaryoplankton communities between March and June. However, principal component analysis showed that the communities were significantly different between the sampling times and sampling sites. Water temperature (WT), oxidation-reduction potential (ORP), water transparency (SD), NO₃-N, and NH₃ significantly influenced bacterioplankton communities, and WT, SD, ORP, and NH₄-N significantly influenced eukaryoplankton communities in the river. These results implied that compared with the sampling sites, sampling times more significantly affected the bacterioplankton and eukaryoplankton river communities by influencing WT, ORP, SD, and nitrogen forms.

Peracetic acid Activity on Biofilm Formed by Escherichia coli Isolated from an Industrial Water System

One of the major problems in industrial water systems is the generation of biofilm, which is resistant to antimicrobial agents and causes failure of sanitization policy. This work aimed to study the anti-biofilm activity of peracetic acid (PAA) at contact times and temperatures combinations. To this end, a 96 well microtiter-based calorimetric method was applied in in vitro biofilm production using Ecsherichia coli, isolated from the water supply system of a pharmaceutical plant. The phenotypic and phylogenetic tests confirmed the isolated bacteria belong to strains of Ecsherichia coli. The anti-biofilm activity of peracetic acid on formed biofilm was investigated at concentrations of 0.15-0.5% for a contact time of 5-15 min at 20°C to 60°C. The maximum biofilm formation by MTP method using an Ecsherichia coli isolate was achieved in 96 h incubation in TSB containing wells at 37°C. Biofilm formation rate showed to be high by the environmental isolate compared with that of standard strain. PAA at concentrations above 0.25%, the temperature of 40°C, and a minimum of 10 minutes of contact time was effective in the eradication of biofilm in an MPT-based system.

Spatial Variation of Cladophora Epiphytes in the Nan River, Thailand

Cladophora is an algal genus known to be ecologically important. It provides habitats for microorganisms known to provide ecological services such as biosynthesis of cobalamin (vitamin B12) and nutrient cycling. Most knowledge of microbiomes was obtained from studies of lacustrine Cladophora species. However, whether lotic freshwater Cladophora microbiomes are as complex as the lentic ones or provide similar ecological services is not known. To illuminate these issues, we used amplicons of 16S rDNA, 18S rDNA, and ITS to investigate the taxonomy and diversity of the microorganisms associated with replicate Cladophora samples from three sites along the Nan River, Thailand. Results showed that the diversity of prokaryotic and eukaryotic members of Cladophora microbiomes collected from different sampling sites was statistically different. Fifty percent of the identifiable taxa were shared across sampling sites: these included organisms belonging to different trophic levels, decomposers, and heterotrophic bacteria. These heterogeneous assemblages of bacteria, by functional inference, have the potential to perform various ecological functions, i.e., cellulose degradation, cobalamin biosynthesis, fermentative hydrogen production, ammonium oxidation, amino acid fermentation, dissimilatory reduction of nitrate to ammonium, nitrite reduction, nitrate reduction, sulfur reduction, polyphosphate accumulation, denitrifying phosphorus-accumulation, and degradation of aromatic compounds. Results suggested that river populations of Cladophora provide ecologically important habitat for microorganisms that are key to nutrient cycling in lotic ecosystems.

Diversity of Aerobic Anoxygenic Phototrophs and Rhodopsin-Containing Bacteria in the Surface Microlayer, Water Column and Epilithic Biofilms of Lake Baikal

The diversity of aerobic anoxygenic phototrophs (AAPs) and rhodopsin-containing bacteria in the surface microlayer, water column, and epilithic biofilms of Lake Baikal was studied for the first time, employing pufM and rhodopsin genes, and compared to 16S rRNA diversity. We detected pufM-containing Alphaproteobacteria (orders Rhodobacterales, Rhizobiales, Rhodospirillales, and Sphingomonadales), Betaproteobacteria (order Burkholderiales), Gemmatimonadetes, and Planctomycetes. Rhodobacterales dominated all the studied biotopes. The diversity of rhodopsin-containing bacteria in neuston and plankton of Lake Baikal was comparable to other studied water bodies. Bacteroidetes along with Proteobacteria were the prevailing phyla, and Verrucomicrobia and Planctomycetes were also detected. The number of rhodopsin sequences unclassified to the phylum level was rather high: 29% in the water microbiomes and 22% in the epilithon. Diversity of rhodopsin-containing bacteria in epilithic biofilms was comparable with that in neuston and plankton at the phyla level. Unweighted pair group method with arithmetic mean (UPGMA) and non-metric multidimensional scaling (NMDS) analysis indicated a distinct discrepancy between epilithon and microbial communities of water (including neuston and plankton) in the 16S rRNA, pufM and rhodopsin genes.

Pseudorhodobacter turbinis sp. nov., isolated from the gut of the Korean turban shell, Turbo cornutus

A novel Gram-stain-negative, coccus-shaped, aerobic and motile bacterial strain, designated S12M18^T, was isolated from the gut of the Korean turban shell, Turbo cornutus. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain S12M18^T belonged to the genus Pseudorhodobacter and had the highest 16S rRNA gene sequence similarity twith Pseudorhodobacter aquimaris HDW-19^T (98.63 %). The phylogenomic tree congruently verified that strain S12M18^T occupies a taxonomic position within the genus Pseudorhodobacter. The OrthoANIu value between strain S12M18^T and P. aquimaris HDW-19^T was 87.22 %. The major cellular fatty acid of strain S12M18^T was summed feature 8 (C_18 : 1 ω7c or C_18 : 1 ω6c). The major components of the polar lipids were phosphatidylcholine, phosphatidylglycerol and phosphatidylethanolamine. The predominant isoprenoid quinone was Q-10. The DNA G＋C content was 57.8 mol%. The polyphasic analyses indicated that strain S12M18^T represents a novel species of the genus Pseudorhodobacter, for which the name Pseudorhodobacter turbinis sp. nov. is proposed. The type strain is S12M18^T (=KCTC 62742^T=JCM 33168^T).

Tabrizicola oligotrophica sp. nov. and Rhodobacter tardus sp. nov., two new species of bacteria belonging to the family Rhodobacteraceae

Two Gram-stain-negative, aerobic, non-motile bacteria, designated KMS-5^T and CYK-10^T, were isolated from freshwater environments. 16S rRNA gene sequence similarity results indicated that these two novel strains belong to the family Rhodobacteraceae. Strain KMS-5^T is closely related to species within the genus Tabrizicola (96.1-96.8 % sequence similarity) and Cypionkella (96.5-97.0 %). Strain CYK-10^T is closest to Rhodobacter thermarum YIM 73036^T with 96.6 % sequence similarity. Phylogenetic analyses based on 16S rRNA gene sequences and an up-to-date bacterial core gene set showed that strain KMS-5^T is affiliated with species in the genus Tabrizicola and strain CYK-10^T is placed in a distinct clade with Rhodobacter blasticus ATCC 33485^T, Rhodobacter thermarum YIM 73036^T and Rhodobacter flagellatus SYSU G03088^T. These two strains shared common chemotaxonomic features comprising Q-10 as the major quinone, phosphatidylethanolamine, phosphatidylglycerol and phosphatidylcholine as the principal polar lipids, and C_18 : 1  ω7c as the main fatty acid. The average nucleotide identity, average amino acid identity and digital DNA-DNA hybridization values between these two novel isolates and their closest relatives were below the cut-off values of 95-96, 90 and 70 %, respectively, used for species demarcation. The obtained polyphasic taxonomic data suggested that strain KMS-5^T represents a novel species within the genus Tabrizicola, for which the name Tabrizicola oligotrophica sp. nov. is proposed with KMS-5^T (=BCRC 81196^T=LMG 31337^T) as the type strain, and strain CYK-10^T should represent a novel species of the genus Rhodobacter, for which the name Rhodobacter tardus sp. nov. is proposed with CYK-10^T (=BCRC 81191^T=LMG 31336^T) as the type strain.

Tabrizicola algicola sp. nov. isolated from culture of microalga Ettlia sp

A novel Gram-stain-negative, aerobic, non-spore-forming, non-motile, and rod-shaped bacterium, strain ETT8^T was isolated from a chemostat culture of microalga Ettlia sp. YC001. Optimal growth was with 0-2% NaCl and at 25-37 °C on R2A medium. Phylogenetic analysis based on the 16S rRNA gene and genome sequence showed that strain ETT8^T belongs to the genus Tabrizicola, with the close neighbours being T. sediminis DRYC-M-16^T (98.1 %), T. alkalilacus DJC^T (97.6 %), T. fusiformis SY72^T (96.9 %), T. piscis K13M18^T (96.8 %), and T. aquatica RCRI19^T (96.5 %). The genomic comparison of strain ETT8^T with type species in the genus Tabrizicola was analysed using the genome-to-genome distance calculator (GGDC), average nucleotide identity (ANI), and average amino acid identity (AAI) (values indicated ≤17.7, ≤75.4 and ≤71.9 %, respectively). The genomic DNA G+C content of strain ETT8^T was 64.4 %, plus C_18 : 1  ω6c and C_18 : 0-iso were the major fatty acids and Q-10 the major respiratory quinone. Strain ETT8^T contained diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine aminolipid, and four unidentified lipids as the major polar lipids. Based on the chemotaxonomic, genotypic, and phenotype results, strain ETT8^T was recognized as a novel species of the genus Tabrizicola for which the name Tabrizicola algicola sp. nov. is proposed. The type strain is ETT8^T (=KCTC 72206^T=JCM 31893^T=MCC 4339^T).

Polycyclic Aromatic Hydrocarbons Degradation by Aquatic Bacteria Isolated from Khazar Sea, the World’s Largest Lake

Background: Aquatic microorganisms have an important role in the bioremediation of environmental pollutants. Polycyclic Aromatic Hydrocarbons (PAHs) are described as dangerous pollutants that can bind covalently to the nucleic acids, causing mutations. Therefore, they have carcinogenic and toxic properties. Also, are involved in diseases such as asthma, lung dysfunction, and chronic bronchitis. This study aimed to isolate and characterize aquatic bio-degrading bacteria from the world’s largest lake, Khazar, with the ability to use PAHs as only carbon source. Methods: Samples were taken from the estuary of Siah Rud River (Mazandaran province, Iran) and Fereydunkenar beach leading to isolation of twenty-three bacteria on marine agar and sea water media. The isolates were cultured on separate ONR7a medium, each supplemented with only one PAH; as the sole carbon source; including naphthalene, phenanthrene, and anthracene. Results: Eleven bacterial isolates were able to grow on supplemented media: TBZ-E1, TBZ-E2, TBZ-E3, TBZ-S12, TBZ-S16, TBZ-E20, TBZ-SF2, TBZ-F1, TBZ-F2, TBZ-F3 and TBZ2. These isolates belong to Alteromonas, Marivivens, Pseudoalteromonas, Vibrio, Shewanella, Photobacterium, Mycobacterium and Pseudomonas genera. The qualitative analysis showed that the consortium of isolates TBZ-F1, TBZ-F2, TBZ-F3, TBZ-SF2, and TBZ2 displayed the highest degradation rate for phenanthrene and naphthalene. Naphthalene, phenanthrene, and anthracene were potently degraded by TBZ2 and TBZ-SF2 and accordingly were subjected to measure degradation potential of mentioned PAHs. Conclusion: The bacterial isolates of Caspian lake have a critical duty in biodegradation of PAHs. These isolates are representative samples of the bacterial population of this lake, participating in the purification process of this habitat.

Tabrizicola piscis sp. nov., isolated from the intestinal tract of a Korean indigenous freshwater fish, Acheilognathus koreensis

A novel Gram-negative, obligately aerobic, rod-shaped and non-motile bacterium, designated strain K13M18T, was isolated from the intestinal tract of a Korean indigenous fish, oily bitterling (Acheilognathus koreensis). Strain K13M18T formed creamy-pink colonies on a marine agar plate. Results of phylogenetic analysis based on the 16S rRNA gene sequence similarity indicated that strain K13M18T was most closely related to Tabrizicola sediminis DRYC-M-16T, sharing 97.62 % similarity with that strain. Strain K13M18T belonged to the genus Tabrizicola , which formed a cluster with Tabrizicola aquatica RCRI19T, Tabrizicola fusiformis SY72T, Tabrizicola sediminis DRYC-M-16T and Tabrizicola alkalilacus DJCT in a phylogenetic tree based on the 16S rRNA gene sequences. Strain K13M18T grown optimally in 0 % (w/v) NaCl, at pH 7 and 30 °C, in a marine broth medium. The predominant cellular fatty acids were C18 : 1 ω7c and C18 : 1 ω6c. The major respiratory isoprenoid quinone was ubiquinone Q-10. Polar lipids of strain K13M18T contained phosphatidylcholine, phosphatidylglycerol, phosphatidylinositol, diphosphatidylglycerol, six unidentified aminophospholipids, one unidentified aminolipid and an unidentified lipid. Based on genome sequencing, the DNA G+C content of strain K13M18T was 64.08 mol %, with an average nucleotide identity value, calculated by a comparative genomic analysis of strains K13M18T and T. sediminis DRYC-M-16T, of 74.82 %. Based on the phylogenetic, genotypic, and phenotypic information, strain K13M18T is proposed to be a novel species of the genus Tabrizicola . The type strain is K13M18T (=KCTC 62659T=JCM 33230T).

Antibacterial and Antifungal Activity of Novel Freshwater Bacterium Tabrizicola aquatica as a Prominent Natural Antibiotic Available in Qurugol Lake

Background : Recently, resistant pathogenic microorganisms have become increasingly wide spread. The search for new natural antibiotics is a viable solution to this problem. For this aim we investigated the antimicrobial ability of Tabrizicola aquatica, the novel bacterium isolated from Qurugol Lake located nearby Tabriz city, Iran. Methods: The antimicrobial properties of Tabrizacola aquatica was investigated using well diffusion test. Tabtizicola aquatica was incubated at 40℃ in shaking incubator at 150 rpm for 14 days. The culture was centrifuged to obtain cell free supernatant, which was sterilized using 0.2 μm filter paper and lyophilized. Microorganisms were lawn and then wells were prepared over the agar plates. About 100 ml of the diluted lyophilized supernatant was added to the wells. The plates then were incubated at 37℃. After 48 hours, antimicrobial activity was defined by measuring the inhibition zone diameter. Results: The bacterial filtrates had considerable antagonistic effect against Escherichia coli, Rhizobium radiobacter, Pseudomonas syringae, Erwinia amylovora, Botrytis cinerea, Neurospora crassa and Fusarium oxysporum. However, the filtrates did not show any inhibitory action on the Aspergillus flavus and Klebsiella pneumonia. The supernatant decreased the growth zone on Streptococcus aureus, Pseudomonas aeruginosa, Shigella flexneri, Xanthomonas camoestris and Bassilus cereos. The result of MIC against pathogens was found for Neurospora crassa in the 50 µg/mL. Conclusion: The results, suggested that Tabrizicola aquatica and similar bacteria can be helpful to control freshwater natural water sources from pathogenic microorganism. Moreover, microbial natural products are still the most promising source of new antibiotics. Our results point out a scope for characterization of the metabolites and could be a candidate in the identification of novel antibiotics.

Tabrizicola alkalilacus sp. nov., isolated from alkaline Lake Dajiaco on the Tibetan Plateau

A novel Gram-stain-negative, aerobic, non-motile and rod-shaped bacterium was isolated from Lake Dajiaco on the Tibetan Plateau. Strain DJC^T grew without NaCl and tolerated up to 3 % (w/v) NaCl. Growth occurred at pH 6.0-10.0 (optimum, pH 7.0-8.0) and 15-37 °C (optimum, 25-30 °C). Vitamins were not required for growth. The main polar lipids of strain DJC^T were diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine. The predominant respiratory quinone was Q-10. The major fatty acid was C_18 : 1ω7c. Genome sequencing revealed a genome size of 4.61 Mbp and a G+C content of 62.9 mol%. Analysis of 16S rRNA sequences showed that strain DJC^T belonged to the genus Tabrizicola, with the closest neighbour Tabrizicola aquatica RCRI19^T (97.5 %). DNA-DNA relatedness between strain DJC^T and the closest phylogenetically related strain T. aquatica RCRI19^T was 40.8 %. Stain DJC^T was clearly distinguished from the type strain mentioned above through phylogenetic analysis, DNA-DNA hybridization, fatty acid composition data and a range of physiological and biochemical characteristic comparisons. Based on its phenotypic and chemotaxonomic characteristics, strain DJC^T could be classified as a representative of a novel species of the genus for which the name Tabrizicola alkalilacus sp. nov. is proposed. The type strain is DJC^T (=CICC 24242^T=KCTC 62173^T).