Diversity and ecological assembly process of aerobic anoxygenic phototrophic bacteria in a low irradiation area, Three Gorges Reservoir.

Aerobic anoxygenic phototrophic bacteria (AAPB) are significant bacterial groups in aquatic ecosystems, known for their rapid growth and photoheterotrophic characteristics. However, the distribution and ecological assembly process of AAPB in low irradiation freshwater basins remain unclear, warranting further investigation. In this study, we present the diversity, abundance, spatial variations, ecological process, and community interaction of AAPB in sediment of Three Gorges Reservoir (TGR) under low irradiation. Our findings demonstrate the dominant genera of AAPB community that exist in the TGR area also are appeared in different waters, with some regional preference. Moreover, the concentration of pufM gene, an indicator for AAPB, maintains a consistently high numerical level ranging from (2.21 ± 0.44) × 104 to (9.98 ± 0.30) × 107 gene copies/g. Although solar irradiation is suggested as the major factor affecting AAPB, it remains unclear whether and how AAPB differ between regions due to varying solar irradiation levels. Our results show spatial differences between total bacteria and AAPB communities, with significant differences observed only in AAPB. Geographical and environmental factor contributed less than 10% to the spatial difference of community, with sediment type and environmental factors being the key factors influencing microbial community structure. The stochastic process plays a dominant role in the aggregation and replacement of AAPB communities, among which the most contribution is dispersal limitation. For AAPB network, Yoonia and Gemmobacter are the hubs for modules. Those results valuable insights into the AAPB communities in TGR with low irradiation.

Bosea beijingensis sp. nov., Telluria beijingensis sp. nov. and Agrococcus beijingensis sp. nov., isolated from baijiu mash.

The baijiu fermentation environment hosts a variety of micro-organisms, some of which still remain uncultured and uncharacterized. In this study, the isolation, cultivation and characterization of three novel aerobic bacterial strains are described. The cells of strain REN20T were Gram-negative, strictly aerobic, motile and grew at 26-37 °C, at pH 6.0-9.0 and in the presence of 0-5.0   % (w/v) NaCl. The cells of strain REN29T were Gram-negative, strictly aerobic, motile and grew at 15-30 °C, at pH 6.0-9.0 and in the presence of 0-10.0   % (w/v) NaCl. The cells of strain REN33T were Gram-positive, strictly aerobic, motile and grew at 15-37 °C, at pH 5.0-10.0 and in the presence of 0-7.0   % (w/v) NaCl. The digital DNA-DNA hybridization and average nucleotide identity by orthology values between type strains in related genera and REN20T (20.3-36.8 % and 79.8-89.9  %), REN29T (20.3-36.8  % and 74.5-88.5  %) and REN33T (22.6-48.6  % and 75.8-84.2  %) were below the standard cut-off criteria for the delineation of bacterial species, respectively. Based on polyphasic taxonomy analysis, we propose three new species, Bosea beijingensis sp. nov. (=REN20T=GDMCC 1.2894T=JCM 35118T), Telluria beijingensis sp. nov. (=REN29T=GDMCC 1.2896T=JCM 35119T) and Agrococcus beijingensis sp. nov. (=REN33T=GDMCC 1.2898T=JCM 35164T), which were recovered during cultivation and isolation from baijiu mash.

Growth and mortality of aerobic anoxygenic phototrophs in the North Pacific Subtropical Gyre.

Aerobic anoxygenic phototrophic (AAP) bacteria harvest light energy using bacteriochlorophyll-containing reaction centers to supplement their mostly heterotrophic metabolism. While their abundance and growth have been intensively studied in coastal environments, much less is known about their activity in oligotrophic open ocean regions. Therefore, we combined in situ sampling in the North Pacific Subtropical Gyre, north of O'ahu island, Hawaii, with two manipulation experiments. Infra-red epifluorescence microscopy documented that AAP bacteria represented approximately 2% of total bacteria in the euphotic zone with the maximum abundance in the upper 50 m. They conducted active photosynthetic electron transport with maximum rates up to 50 electrons per reaction center per second. The in situ decline of bacteriochlorophyll concentration over the daylight period, an estimate of loss rates due to predation, indicated that the AAP bacteria in the upper 50 m of the water column turned over at rates of 0.75-0.90 d-1. This corresponded well with the specific growth rate determined in dilution experiments where AAP bacteria grew at a rate 1.05 ± 0.09 d-1. An amendment of inorganic nitrogen to obtain N:P = 32 resulted in a more than 10 times increase in AAP abundance over 6 days. The presented data document that AAP bacteria are an active part of the bacterioplankton community in the oligotrophic North Pacific Subtropical Gyre and that their growth was mostly controlled by nitrogen availability and grazing pressure.IMPORTANCEMarine bacteria represent a complex assembly of species with different physiology, metabolism, and substrate preferences. We focus on a specific functional group of marine bacteria called aerobic anoxygenic phototrophs. These photoheterotrophic organisms require organic carbon substrates for growth, but they can also supplement their metabolic needs with light energy captured by bacteriochlorophyll. These bacteria have been intensively studied in coastal regions, but rather less is known about their distribution, growth, and mortality in the oligotrophic open ocean. Therefore, we conducted a suite of measurements in the North Pacific Subtropical Gyre to determine the distribution of these organisms in the water column and their growth and mortality rates. A nutrient amendment experiment showed that aerobic anoxygenic phototrophs were limited by inorganic nitrogen. Despite this, they grew more rapidly than average heterotrophic bacteria, but their growth was balanced by intense grazing pressure.

Phenology and ecological role of aerobic anoxygenic phototrophs in freshwaters.

BACKGROUND: Aerobic anoxygenic phototrophic (AAP) bacteria are heterotrophic bacteria that supply their metabolism with light energy harvested by bacteriochlorophyll-a-containing reaction centers. Despite their substantial contribution to bacterial biomass, microbial food webs, and carbon cycle, their phenology in freshwater lakes remains unknown. Hence, we investigated seasonal variations of AAP abundance and community composition biweekly across 3 years in a temperate, meso-oligotrophic freshwater lake. RESULTS: AAP bacteria displayed a clear seasonal trend with a spring maximum following the bloom of phytoplankton and a secondary maximum in autumn. As the AAP bacteria represent a highly diverse assemblage of species, we followed their seasonal succession using the amplicon sequencing of the pufM marker gene. To enhance the accuracy of the taxonomic assignment, we developed new pufM primers that generate longer amplicons and compiled the currently largest database of pufM genes, comprising 3633 reference sequences spanning all phyla known to contain AAP species. With this novel resource, we demonstrated that the majority of the species appeared during specific phases of the seasonal cycle, with less than 2% of AAP species detected during the whole year. AAP community presented an indigenous freshwater nature characterized by high resilience and heterogenic adaptations to varying conditions of the freshwater environment. CONCLUSIONS: Our findings highlight the substantial contribution of AAP bacteria to the carbon flow and ecological dynamics of lakes and unveil a recurrent and dynamic seasonal succession of the AAP community. By integrating this information with the indicator of primary production (Chlorophyll-a) and existing ecological models, we show that AAP bacteria play a pivotal role in the recycling of dissolved organic matter released during spring phytoplankton bloom. We suggest a potential role of AAP bacteria within the context of the PEG model and their consideration in further ecological models.

In situ assessment of the initial phase of wastewater biofilm formation: Effect of the presence of algae in an aerobic bacterial biofilm system.

The initial start-up attachment stage that dominates biofilm formation is an unstable process and is time-consuming. In the present study, Chlorella sp. was introduced into a general aerobic biofilm system to explore whether the addition of algae improved the initial attachment phase of biofilm. Compared with those of the bacterial biofilms, the initial algal-bacterial biofilms were more stable and had a thicker, denser, and rougher surface. Further investigation suggested that the concentration of extracellular polymeric substances (EPSs) in the algal-bacterial biofilm was 31.33 % greater than that in the bacterial biofilm. Additionally, the algal-bacterial flocs had greater free energies of absolute cohesion (ΔGcoh) and adhesion energy (∆Gadh) than did the bacterial flocs. These phenomena contribute to the speediness and stabilization of initial algal-bacterial start-up biofilms. Specifically, algae inoculation increased microbial community diversity and promoted the growth of bacterial members related to biofilm development. In conclusion, both physicochemical interactions and biological processes strongly influence microbial attachment during the initial biofilm formation process and further promote strengthening.

Cholangitis with bacteremia due to Pseudomonas nitroreducens in a patient with pancreatic neuroendocrine tumors: a case report.

BACKGROUND: Pseudomonas nitroreducens is a non-fermenting, gram-negative, rod-shaped bacterium commonly inhabiting soil, particularly soil contaminated with oil brine. To our knowledge, no cases of human infection with P. nitroreducens have been previously reported. Here, we present the first documented case of cholangitis caused by P. nitroreducens in a patient with bacteremia. CASE PRESENTATION: A 46-year-old Japanese man with an advanced pancreatic neuroendocrine tumor was hospitalized with fever and chills. Four days before admission, the patient developed right upper abdominal pain. Two days later, he also experienced fever and chills. Endoscopic retrograde cholangiopancreatography was performed on the day of admission, and the patient was diagnosed as having cholangitis associated with stent dysfunction. Gram-negative rods were isolated from blood cultures, but attempts to identify the bacteria using VITEK2 and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) with VITEK MS ver. 4.7.1 (bioMérieux Japan Co. Ltd., Tokyo, Japan) were unsuccessful. Finally, the organism was identified as P. nitroreducens using MALDI-TOF MS with a MALDI Biotyper (Bruker Daltonics Co., Ltd., Billerica, MA, USA) and 16 S ribosomal RNA sequencing. Despite thorough interviews with the patient, he denied any exposure to contaminated soil. The patient was treated with intravenous cefepime and oral ciprofloxacin for 16 days based on susceptibility results, achieving a good therapeutic outcome. At the outpatient follow-up on day 28, the patient was in good general condition. CONCLUSIONS: This is the first reported human case of cholangitis with bloodstream infection caused by P. nitroreducens. This report provides clinicians with novel insights into the clinical manifestations and diagnostic methods necessary for the accurate diagnosis of P. nitroreducens, along with guidance on treatment.

Enhanced nitrate removal efficiency and microbial response of immobilized mixed aerobic denitrifying bacteria through biochar coupled with inorganic electron donors in oligotrophic water.

The nitrogen removal characteristics and microbial response of biochar-immobilized mixed aerobic denitrifying bacteria (BIADB) were investigated at 25 °C and 10 °C. BIADB removed 53.51 ± 1.72 % (25 °C) and 39.90 ± 4.28 % (10 °C) nitrate in synthetic oligotrophic water. Even with practical oligotrophic water, BIADB still effectively removed 47.66-53.21 % (25 °C), and 39.26-45.63 % (10 °C) nitrate. The addition of inorganic electron donors increased nitrate removal by approximately 20 % for synthetic and practical water. Bacterial and functional communities exhibited significant temperature and stage differences (P < 0.05), with temperature and total dissolved nitrogen being the main environmental factors. The dominant genera and keystone taxa exhibited significant differences at the two temperatures. Structural equation model analysis showed that dissolved organic matter had the highest direct and indirect effects on diversity and function, respectively. This study provides an innovative pathway for utilizing biochar and inorganic electron donors for nitrate removal from oligotrophic waters.

Comparison of moving bed biofilm reactor and bio-contact oxidation reactor start-up with heterotrophic nitrification-aerobic denitrification bacteria and activated sludge inoculation under high ammonia nitrogen conditions.

To overcome poor ammonia tolerance and removal performance of bio-contact oxidation (BCO) reactor inoculated with activated sludge for high-ammonia nitrogen (NH4+-N) chemical wastewater treatment, this study compared inoculating heterotrophic nitrification-aerobic denitrification (HN-AD) bacteria in moving bed biofilm reactor (MBBR) with activated sludge inoculation in BCO reactor under simulated high NH4+-N conditions. Results revealed that MBBR achieved faster biofilm formation (20 days vs. 100 days for BCO) with notable advantages: 27.6 % higher total nitrogen (TN) and 29.9 % higher NH4+-N removal efficiency than BCO. Microbial analysis indicated optimal enrichment of the key nitrogen removal (NR) bacterium Alcaligenes, leading to increased expression of NR enzymes hydroxylamine reductase, ensuring the superior NR efficiency of the MBBR. Additionally, functional enzymes and genes analysis speculated that the NR pathway in MBBR was: NH4+-N â†’ NH2OH â†’ NO3--N â†’ NO2--N â†’ NO â†’ N2O â†’ N2. This research offers a practical and theoretical foundation for extending HN-AD bacteria-inoculated MBBR processes.

Screening and diversity of culturable HNAD bacteria in the MBR sewage treatment system.

The activated sludge was collected from the Membrane BioReactor (MBR) pool of the sewage treatment system of Sanxing Town, Jintang County, Chengdu, to obtain a good population of heterotrophic nitrifying/aerobic denitrifying (HNAD) bacteria. After undergoing enrichment, isolation, and purification, the HNAD bacteria were selected using the pure culture method. The 16S rDNA molecular technology was used to determine the taxonomy of bacteria. The heterophic nitrifying ability and denitrification capacity of HNAD strains was ascertained through their growth characteristics in heterotrophic nitrification and denitrification media. The results showed that 53 HNAD strains selected from the MBR pool belonged to 2 phyla, 3 classes, 6 orders, 6 families, and 7 genera, with 26 species. Acinetobacter was the largest and dominant genus. Among these, strains numbered (bacterial strain) SW21HD14, SW21HD17, and SW21HD18 were potentially new species in the Acinetobacter genus. Each HNAD strain showed a significant heterotrophic nitrifying and aerobic denitrifying efficiency compared with the control strain (P < 0.05). Specifically, 10 strains demonstrated ammonia nitrogen degradation of greater than 70 mg·L-1 and 9 strains demonstrated nitrate nitrogen degradation above 150 mg·L-1. The HNAD bacteria, which were selected from the MBR pool of sewage treatment system of the Sanxing Town sewage treatment plant, exhibited rich diversity and strong nitrogen removal ability. These findings offered an effective strain source and theoretical basis for implementing biological denitrification technology that involves synchronous nitrification and denitrification.

Ventilator-associated pneumonia by Weeksella virosa: case report.

BACKGROUND: Weeksella virosa pneumonia is an infection that has been described as a healthcare-associated infection. This is a rare gram-negative anaerobic bacterium associated with the use of mechanical ventilation for a long period of time and is more frequent in immunosuppressed patients. This is the first case reported in the state of Veracruz and the second in Mexico. CASE PRESENTATION: We present the case of a 64-year-old female from Veracruz, Mexico who developed an infectious process in the right pelvic limb after a transcatheter aortic valve replacement procedure and subsequently developed sudden cardiorespiratory arrest requiring mechanical ventilation, with subsequent imaging studies demonstrating a pneumonic process associated with a nosocomial infection. DISCUSSION AND CONCLUSIONS: We should take into consideration that this pathogen affects not only adults with multiple comorbidities but also children with renal, hepatic, or oncological pathologies, as well as immunocompromised patients, who should be considered high-risk populations for W. virosa infection.

Nitrogen removal efficiency and mechanisms of an improved anaerobic-anoxic-oxic system for decentralized sewage treatment.

The unstable operation and poor effluent quality often associated with decentralized sewage treatment systems due to fluctuating water flows have garnered significant attention. In this study, a novel integrated process combining anoxic denitrification and simultaneous nitrification and denitrification was developed to address these challenges. The improved anaerobic-anoxic-aerobic system achieved average effluent concentrations of 20.83 mg/L and 4.63 mg/L for chemical oxygen demand and NH4+-N, with average removal rates of 91 % and 68 %, respectively. Moreover, the aerobic zone demonstrated an impressive efficiency of 40.8 % for simultaneous nitrification and denitrification. The key bacteria groups driving the system's performance were heterotrophic and aerobic nitrifying bacteria, which dominated the microbial populations. Overall, the system optimizes the traditional anaerobic-anoxic-aerobic process, providing an effective solution for fluctuating wastewater flows. It establishes a successful coexistence model for multiple microbial populations, highlighting its applicability for superior nitrogen removal performance, and reference for optimizing rural sewage treatment. TAKE HOME MESSAGE SENTENCE: The improved anaerobic-anoxic-aerobic system for fluctuating wastewater treatment has superior nitrogen removal performance depending on multiple microbial populations.

Effect of non-thermal ultraviolet and ultrasound technologies on disinfection of meat preparation equipment in catering industry.

In recent years, ultraviolet and ultrasound treatments are gaining attraction as promising green decontamination technologies to ensure microbial safety in food industry. Decontamination by ultraviolet light is a physical process defined by the transfer of electromagnetic energy from a light source to an organism's cellular material and depended on the emission of radiation in the ultraviolet region (100-400 nm), specifically the UV-C region (200-280 nm) which has been demonstrated to be germicidal. Ultrasound technology is defined as sound waves with high and low frequency beyond the limit of human hearing and shows a decontamination effect that occurs as a consequence of cavitation at high power (low frequency) in general. In the present study, it was aimed to determine the effectiveness of ultraviolet light (254 nm, 10 min) and high frequency ultrasound techniques (40 kHz, 10 min) in reducing total aerobic mesophilic bacteria, yeast and mold, Esherichia coli/coliform and Salmonella spp. on the equipment surfaces used in the catering facility. For this purpose, the equipment (cutting knife, meat grinder knife, knife sharpener, cut-proof glove) used in the meat preparation department of catering facility were selected for the treatments. According to the results, appreciable reductions were achieved in total aerobic mesophilic bacterial counts of the ultraviolet treated samples (maximum difference 2.61 log cfu/cm2) and the ultrasound treated samples (maximum difference 4.07 log cfu/cm2). After ultraviolet treatment, Salmonella spp. were totally inhibited on the contaminated surfaces. Furthermore, Escherichia coli/coliform was not detected in the samples after both treatments whereas it was detected before the treatments. It has been concluded that the techniques are effective in reducing microbiological load and also ultraviolet treatment is effective on pathogenic microorganisms on food contact surfaces. As a result, the ultraviolet and ultrasound techniques are effective treatments for equipment disinfection in the catering sector and can be used industrially as it gives successful results.

Validation of the FSTestTM Aerobic Count Plates Method for Enumeration of Aerobic Bacteria in a Variety of Matrixes and Stainless Steel Environmental Surface: AOAC Performance Tested MethodSM 112301.

BACKGROUND: The FSTestTM Aerobic Count (AC) Plates are ready-to-use culture media containing nutrients, a cold-water-soluble gelling agent, and a chromogenic indicator. OBJECTIVE: The objective of this study was to validate the FSTest AC plate method for AOAC INTERNATIONAL Performance Tested MethodsSM (PTM) certification for a variety of foods and stainless steel. METHODS: The performance of the FSTest AC plates were compared to the appropriate reference method, for the detection of total aerobic bacterial in a variety of foods matrixes (raw ground beef, raw ground pork, cooked ham, raw chicken breast, raw shrimp, frozen tuna, shredded bagged lettuce, cherry tomato, pasteurized liquid milk, nonfat milk powder) and on stainless steel surfaces. Robustness, consistency, and stability studies of the FSTest AC plate were also conducted. RESULTS: The results of the matrix study showed the standard deviation of repeatability (sr) was similar in both the FSTest AC plate method and the reference method. The 90% confidence interval of the difference between means between the two methods was found to fall within -0.5 to 0.5 log10 for all matrixes at all levels in the method developer and independent laboratory studies. The data in the report also support that the FSTest AC plate method is robust, manufactured in a consistent manner, and can be stable for 18 months at 4-10°C. CONCLUSIONS: The FSTest AC method is validated to be equivalent to the appropriate reference methods for the enumeration of aerobic bacteria in a variety of food matrixes and on stainless steel surfaces at 36 ± 1°C, and 32 ± 1°C (for dairy matrixes) in 24 ± 1 h. HIGHLIGHTS: The FSTest AC plate method offers the advantage of saving labor, space, and time, as results are available within 24 h for all tested matrixes.

Application of pressurized steam and forced hot air for cleaning broiler transport container flooring.

In the United States, cleaning poultry transport containers prior to arrival at the broiler grow-out farm is not currently a widely adopted practice in the industry. However, previous studies have shown that transport containers have an important role in cross-contamination before the broilers arrive at the processing plant. The objective of this study was to evaluate the efficacy of pressurized steam followed by forced hot air to clean transport container flooring and compare it to conventional cleaning procedures. Fiberglass and plastic flooring were cut into even pieces and inoculated with chicken intestinal contents containing Salmonella Infantis or Campylobacter jejuni. The cleaning treatments were pressurized steam, forced hot air, pressurized steam followed by forced hot air, water pressure washing, water pressure washing before and after disinfectant, and no cleaning. Counts for Salmonella, Campylobacter, Escherichia coli, coliforms, and aerobic bacteria were assessed. All reductions were made in comparison to noncleaned samples. Forced hot air applied by itself was not efficient in reducing Campylobacter, coliforms, and E. coli; and limited reductions (less than 1 log10 CFU/cm2) were observed for Salmonella and aerobic bacteria. Then, for all bacteria types evaluated, pressurized steam by itself showed reductions of 2.4 to 3.5 log10 CFU/cm2. Samples that were cleaned with a single-pressure water wash showed reductions of 4.0 to 4.6 log10 CFU/cm2 for all bacteria types. For Salmonella, Campylobacter, and E. coli, the greatest reductions were observed when samples were cleaned with pressurized steam followed by forced hot air (4.3-6.1 log10 CFU/cm2) or water washed before and after disinfectant (4.5-6.2 log10 CFU/cm2), and these treatments did not differ from each other. Pressurized steam followed by forced hot air was shown to be an efficient cleaning procedure to reduce poultry-associated pathogens on transport cage flooring, with the benefit of using less water than conventional water cleaning. Processors may be able to adapt this process to reduce potential cross-contamination and lessen the level of pathogens entering the processing plant.

Vaginal aerobic bacteria of healthy bitches and those with fertility problems.

The most common problems in veterinary practice in bitches are bacterial infections of the reproductive tract associated with fertility problems. Research to determine the correlation between the health status of female dogs and bacterial flora of the genital tract has been ongoing for years, but the results obtained by different authors are often contradictory, and do not always concern breeding bitches. Our study identified the most common aerobic bacteria in the genital tract of numerous breeding bitches population. A total of 275 breeding dogs in anestrous phase of the estrous cycle were included in this study. 198 were qualified to the first group with no genital tract infections and no reproductive disorders. 68 bitches were qualified to the second group with complications such as: infertility, abortion, foetus resorptions and newborn mortality. The type of bacterial isolates was almost the same in the healthy bitches and the group with fertility problems. The most common bacteria obtained from the vaginal tract of the tested dogs were Streptococcus spp., Staphylococcus spp., Mycoplasma canis and Escherichia coli. There were no significant differences in bacterial prevalence in the group with reproductive problems versus healthy dogs; however, we found a statistically significant difference between both groups when the numbers of bacterial strains were compared. The number of one-strain bitches was statistically higher in the problematic group than in the non-problematic one. Bacterial culturing of vaginal swab specimens from breeding bitches without clinical signs of genital disease is of little value. Furthermore, it should always be preceded by an examination (clinical, cytological or vaginoscopy etc.). The request or requirement to perform vaginal cultures that is made by some breeders, while common, is not diagnostic for any pathologic condition and the results of these cultures should never be used to determine if antibiotic therapy is indicated.

Catheter-related bloodstream infection caused by Tsukamurella tyrosinosolvens identified by secA1sequencing in an immunocompromised child: a case report.

BACKGROUND: Tsukamurella spp. are obligate aerobic, gram-positive, non-motile, and slightly acid-fast bacilli belonging to the Actinomycetes family. They share many characteristics with Nocardia, Rhodococcus, Gordonia, and the rapidly growing Mycobacterium species. Therefore, standard testing may misidentify Tsukamurella spp. as another species. Accurate and rapid diagnosis is critical for proper infection management, but identification of this bacterium is difficult in the standard laboratory setting. CASE PRESENTATION: A bloodstream infection caused by a gram-positive bacterium and related to a central venous catheter was identified in an immunocompromised 2-year-old girl. Tsukamurella tyrosinosolvens was identified by modified secA1 sequencing. Antibiotic treatment and removal of the central venous catheter resolved the infection. Inappropriate management of the catheter during an overnight stay outside of the hospital was considered as a possible source of infection. CONCLUSIONS: SecA1 sequencing may be a useful diagnostic tool in the identification of T. tyrosinosolvens. Providing proper central venous catheter care instructions to patients, their families, and medical staff is important for infection prevention.

The impact of primary colonizers on the community composition of river biofilm.

As a strategy for minimizing microbial infections in fish hatcheries, we have investigated how putatively probiotic bacterial populations influence biofilm formation. All surfaces that are exposed to the aquatic milieu develop a microbial community through the selective assembly of microbial populations into a surface-adhering biofilm. In the investigations reported herein, we describe laboratory experiments designed to determine how initial colonization of a surface by nonpathogenic isolates from sturgeon eggs influence the subsequent assembly of populations from a pelagic river community, into the existing biofilm. All eight of the tested strains altered the assembly of river biofilm in a strain-specific manner. Previously formed isolate biofilm was challenged with natural river populations and after 24 hours, two strains and two-isolate combinations proved highly resistant to invasion, comprising at least 80% of the biofilm community, four isolates were intermediate in resistance, accounting for at least 45% of the biofilm community and two isolates were reduced to 4% of the biofilm community. Founding biofilms of Serratia sp, and combinations of Brevundimonas sp.-Hydrogenophaga sp. and Brevundimonas sp.-Acidovorax sp. specifically blocked populations of Aeromonas and Flavobacterium, potential fish pathogens, from colonizing the biofilm. In addition, all isolate biofilms were effective at blocking invading populations of Arcobacter. Several strains, notably Deinococcus sp., recruited specific low-abundance river populations into the top 25 most abundant populations within biofilm. The experiments suggest that relatively simple measures can be used to control the assembly of biofilm on the eggs surface and perhaps offer protection from pathogens. In addition, the methodology provides a relatively rapid way to detect potentially strong ecological interactions between bacterial populations in the formation of biofilms.

Empedobacter sedimenti sp. nov., isolated from sediment of East Taihu Lake.

A Gram-reaction-negative, strictly aerobic, pale yellow, non-gliding, rod-shaped bacterium, designated DT-LB-19T, was isolated from the sediment of East Taihu Lake in Jiangsu Province, PR China. Strain DT-LB-19T showed the highest 16S rRNA gene sequence similarities to members of the genera Algoriella, Chishuiella and Empedobacter (94.84-95.77 %) in the family Weeksellaceae. In phylogenetic trees based on genomes, strain DT-LB-19T clustered within the genus Empedobacter but formed a separate subclade with a high bootstrap value. The average nucleotide identity and digital DNA-DNA hybridization values between DT-LB-19T and the closely related type strains were in the range of 82.5-86.9 % and 25.8-32.3 %, respectively. The major cellular fatty acids were iso-C15 : 0, iso-C17 : 0 3-OH, C16 : 1 ω5c, C16 : 0, summed feature 4 (iso-C17 : 1 I and/or anteiso-C17 : 1 B), summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c) and iso-C15 : 03-OH. The predominant menaquinone was menaquinone-6. The polar lipid profile consisted of phosphatidylethanolamine, one glycolipid, two aminophospholipids and five unidentified lipids. The DNA G+C content was 31.8 mol%. Based on the phenotypic, chemotaxonomic, phylogenetic and genomic results, we propose that strain DT-LB-19T represents a novel species of the genus Empedobacter, for which the name Empedobacter sedimenti sp. nov. is proposed, with strain DT-LB-19T (=KCTC 82330T=CCTCC AB 2023026T= JSACC 11448T) as the type strain.

Nocardioides cremeus sp. nov., Nocardioides abyssi sp. nov. and Nocardioides oceani sp. nov., three actinobacteria isolated from Western Pacific Ocean sediment.

Three Gram-stain-positive, non-motile, short rod-shaped, catalase-positive and oxidase-negative actinomycete strains (SOB44T, SOB72T and SOB77T) were isolated from a deep-sea sediment sample collected from the Western Pacific Ocean. Cells of the three strains showed optimum growth at 30 °C and pH 7.0. Strains SOB44T, SOB72T and SOB77T could tolerate up to 10, 9 and 9 % (w/v) NaCl concentration and grow at pH 5.0-12.0, 5.0-11.0 and 5.0-11.0, respectively. Phylogenetic results based on 16S rRNA gene sequences showed that the three isolates belonged to the genus Nocardioides and were identified as representing three novel species based on 78.0-93.1 % average nucleotide identity and 21.3-50.0 % DNA-DNA hybridization values with closely related reference strains. Strains SOB44T, SOB72T and SOB77T showed highest 16S rRNA gene sequence similarity to Nocardioides salarius CL-Z59T (99.2 %), Nocardioides deserti SC8A-24T (99.2 %) and Nocardioides marmotae zg-579T (98.5 %), respectively. All three strains had MK-8(H4) as the respiratory quinone, iso-C16 : 0 as the major fatty acid, and phosphatidylglycerol, diphosphatidylglycerol and phosphatidylinositol as the major polar lipids. The diagnostic diamino acid in the cell-wall peptidoglycan of all three isolates was ll-diaminopimelic acid. The DNA G+C contents of strains SOB44T, SOB72T and SOB77T were 71.1, 72.9 and 72.9 mol%, respectively. Based on the phenotypic, phylogenetic and genotypic data, strains SOB44T, SOB72T and SOB77T clearly represent three novel taxa within the genus Nocardioides, for which the names Nocardioides cremeus sp. nov. (type strain SOB44T=JCM 35774T= MCCC M28400T), Nocardioides abyssi sp. nov. (type strain SOB72T=JCM 35775T=MCCC M28318T) and Nocardioides oceani sp. nov. (type strain SOB77T=JCM 35776T=MCCC M28544T) are proposed.

Paenimyroides aestuarii gen. nov. sp. nov., a novel bacterium isolated from sediment in the Pearl River Estuary and reclassification of five Flavobacterium and four Myroides species.

An aerobic, Gram-negative, non-motile, yellow-to-orange pigmented and round bacterium, designated strain SCSIO 72103T, was isolated from sediment collected in the Pearl River Estuary, Guangdong Province, PR China and subjected to a polyphasic taxonomic study. Growth occurred at 20-37 °C (optimum, 28 °C), pH 6-8 (optimum, pH 7) and with 1-5.5% NaCl (optimum, 1-3 %). Comparative 16S rRNA gene analysis indicated that strain SCSIO 72103T had the highest similarities to Flavobacterium baculatum SNL9T (94.7 %) and Myroides aquimaris SW105T (94.2 %). Phylogenetic analysis based 16S rRNA gene sequences showed that strain SCSIO 72103T formed a single clade with M. aquimaris SW105T. Strain SCSIO 72103T contained iso-C15 : 0 as the major fatty acid and the predominant respiratory quinone was menaquinone MK-6. These characteristics are consistent with those of F. baculatum SNL9T and M. aquimaris SW105T. Phosphatidylethanolamine, most notably, unidentified aminolipid and unidentified aminophospholipid were major polar lipids. Strain SCSIO 72103T had a single circular chromosome of 2.96 Mb with a DNA G+C content of 35.1 mol%. The average nucleotide identity, average amino acid identity (AAI) and digital DNA-DNA hybridization values showed that the pairwise similarities between SCSIO 72103T and the type strains of F. baculatum SNL9T and M. aquimaris SW105T were 78.5-80.5 %, 79.0-81.4 % and 22.7-22.8 %, respectively. The AAI values between species in this clade and the type species of Flavobacterium and Myroides were below the 65 % threshold, indicating that these species belong to a novel genus. On the basis of phylogenetic, physiological and chemotaxonomic characteristics, strain SCSIO 72103T represents a new species of a novel genus, for which the name Paenimyroides aestuarii gen. nov. sp. nov. is proposed. The type strain is SCSIO 72103T (=KCTC 92043T=MCCC 1K06659T). It is also proposed that nine known species in the genera Flavobacterium and Myroides are reclassified as Paenimyroides species.