Obligate Aerobic Bacteria Research Articles

Efficient butanol production from sweet sorghum stem juice by a co-culture system at an optimum temperature: Insights from oxidation-reduction potential monitoring and pilot scale validation

A two-stage co-culture approach was employed in an acetone-butanol-ethanol (ABE) fermentation. An obligate aerobic bacterium, Arthrobacter sp., was first grown for 6 h at 30 °C to create anaerobic conditions. Subsequently, Clostridium beijerinckii TISTR 1461 was inoculated and a fermentation was performed at 37 °C. To identify an intermediate temperature suitable for both microorganisms, their growth was examined at 30, 34, and 37 °C. C.beijerinckii exhibited the highest specific growth rate at 37 °C, while Arthrobacter sp. displayed similar growth rates at all tested temperatures. Butanol production from a synthetic medium (P2 medium) by C. beijerinckii at different temperatures using oxygen-free nitrogen (OFN) gas flushing as a control treatment revealed that fermentation at 37 °C gave the highest butanol concentration (PB, 9.98 g/L). Consequently, 37 °C was chosen for butanol production from sweet sorghum stem juice (SSJ) by co-culture of these two microorganisms in 1-L screw–capped bottles. Compared to the control treatment, higher PB (11.38 g/L), yield (YB/S, 0.37 g/g) and productivity (QB, 0.24 g/L·h) were achieved using the co-culture system. These results were further confirmed by monitoring the oxidation–reduction potential (ORP) during ABE fermentation in a 2-L stirred-tank bioreactor (STR). Moreover, when the co-culture fermentation at 37 °C was scaled up in a 30-L STR, the PB, YB/S and QB values were comparable to those obtained in the 2-L STR. Therefore, co-culture fermentation of Arthrobacter sp. and C.beijerinckii TISTR 1461 at 37 °C represents a promising method for large-scale butanol production.

One year experience of Achromobacter bacteremia at a tertiary care hospital in Northern India.

Achromobacter is a Gram-negative, motile, obligate aerobic and non-fermentative bacterium. It is an emerging pathogen in the hospital environment as it is frequently found in various solutions. Information about the incidence and risk factors of Achromobacter bacteremia from India is limited. We conducted this study to identify the risk factors and underlying conditions predisposing to bacteremia by Achromobacter spp. and analyse the antibiotic resistance pattern of the isolates. We performed a retrospective observational study where automated blood cultures positive for Achromobacter spp. were assessed for clinical characteristics and antibiotic susceptibility patterns from January 2022 to December 2022 in the microbiology laboratory of a tertiary care centre in Northern India. A total of 14 cases (14/2435, 0.57 %) of Achromobacter spp. were identified from bloodstream infections in one year. The mean age of the patients was 37.59±23.17 years with a male predominance (8/14, 57.1 %). All patients were managed on intravenous antibiotics and intravenous access as peripheral line catheters and only 5(5/14, 35.7 %) patients were managed on central line catheters. The isolates were found highly susceptible to ticarcillin-clavulanic acid (14/14, 100.0 %) followed by fluoroquinolones (12/14, 85.72 %) and trimethoprim-sulphamethoxazole (12/14, 85.72 %). Only 57.14 % (8/14, 57.14 %) of the patients were susceptible to piperacillin-tazobactam. The all-cause 40 day mortality was observed in 35.7 % (5/14, 35.7 %) with two deaths that were directly attributable to sepsis. This study provides insight into the incidence of Achromobacter bacteremia at our centre and the necessary antibiotic therapy to combat it.

A Very Rare Pathogen of Osteomyelitis: Alcaligenes faecalis.

To the Editors: Alcaligenes faecalis is a Gram-negative, rod-shaped, oxidase-positive, catalase-positive, obligate aerobic, motile and nonfermenting bacteria.1 It is commonly found in the environment (soil or water) and in the human gut.2A. faecalis has been associated with various infections such as bacteremia, meningitis, endophthalmitis, endocarditis, skin and soft tissue infections, urinary tract infections, peritonitis, otitis media and pneumonia.3 Here, we present 2 patients with osteomyelitis due to A. faecalis, a rarely reported clinical condition in the literature. Patient 1: An 18-year-old female with a medical history of operated for meningomyelocele and pes cavus was admitted with worsening pain in her right lower extremity. On admission, she was afebrile with normal vital signs there was a chronic ulcerated wound with seropurulent discharge on the right foot. On the laboratory evaluation, there was no leukocytosis, C-reactive protein, and procalcitonin were negative, erythrocyte sedimentation rate was 35 mm/h. Clindamycin 30 mg/kg/d and cefotaxime 200 mg/kg/d intravenously (IV) were administered empirically. The contrast-enhanced magnetic resonance imaging showed cellulitis in soft tissue and osteomyelitis in the bone at the level of the 5th finger metatarsal base and proximal shaft (Fig. 1). Wound debridement was performed by orthopedics. She developed emesis and rash on day 4 and the antibiotic was changed to IV ciprofloxacin (30 mg/kg/d). Intraoperative wound culture grew A. faecalis which was sensitive to ampicillin, cefotaxime and gentamicin. Due to clinical improvement, treatment with ciprofloxacin continued and she was discharged after 15 days of IV therapy. The total treatment is planned to be completed in 8 weeks.FIGURE 1.: MRI (T2 weighted) showing osteomyelitis of the right foot. MRI indicates magnetic resonance imaging.Patient 2: A 15-year-old girl presented with a chronic ulcerated wound on her right foot. She had been operated twice for meningomyelocele and had pes planovalgus. She was afebrile and there was a chronic wound without any discharge on her right foot on admission. Laboratory evaluation revealed negative acute phase reactants and erythrocyte sedimentation rate was 24 mm/h. The empirical treatment was administered as IV cefotaxime and clindamycin. The contrast-enhanced magnetic resonance imaging showed findings suggestive of active osteomyelitis on the right calcaneus (Fig. 1). Orthopedics performed wound debridement and inserted vacuum-assisted closure therapy system. A. faecalis growth was detected in the tissue culture which was sensitive to ceftazidime and meropenem but resistant to amikacin. Her treatment was changed to IV ceftazidime (150 mg/kg/d). After vacuum-assisted closure treatment, it was planned to perform tissue repair by plastic surgery and to continue antibiotherapy IV due to the resistance pattern of the microorganism. Opportunistic infections and antimicrobial resistance associated with A. faecalis have been reported but osteomyelitis due to A. faecalis was documented in a few patients with diabetic foot ulcers in the literature.4 It is usually sensitive to beta-lactam antibiotics and trimethoprim/sulfamethoxazole and resistant to aminoglycosides and tetracyclines.5 Most of the previously documented cases have been successfully treated with amoxicillin/clavulanic acid but antibiotic resistance is an emerging problem. In summary, we present 2 patients with osteomyelitis due to A. faecalis, a rare cause of osteomyelitis. In addition to surgery, medical treatment should be arranged based on the antibiotic susceptibility results for successful and appropriate treatment.

Analysis of Myxococcus xanthus Vegetative Biofilms With Microtiter Plates.

The bacterium Myxococcus xanthus forms both developmental and vegetative types of biofilms. While the former has been studied on both agar plates and submerged surfaces, the latter has been investigated predominantly on agar surfaces as swarming colonies. Here we describe the development of a microplate-based assay for the submerged biofilms of M. xanthus under vegetative conditions. We examined the impacts of inoculation, aeration, and temperature to optimize the conditions for the assay. Aeration was observed to be critical for the effective development of submerged biofilms by M. xanthus, an obligate aerobic bacterium. In addition, temperature plays an important role in the development of M. xanthus submerged biofilms. It is well established that the formation of submerged biofilms by many bacteria requires both exopolysaccharide (EPS) and the type IV pilus (T4P). EPS constitutes part of the biofilm matrix that maintains and organizes bacterial biofilms while the T4P facilitates surface attachment as adhesins. For validation, we used our biofilm assay to examine a multitude of M. xanthus strains with various EPS and T4P phenotypes. The results indicate that the levels of EPS, but not of piliation, positively correlate with submerged biofilm formation in M. xanthus.

Butanol Production by a Novel Efficient Method Using Mixed Cultures of Clostridium beijerinckii and Arthrobacter sp. in Stirred-Tank and Gas-Lift Bioreactors

Arthrobacter sp. BCC 72131, an obligate aerobic bacterium, was used to create anaerobic conditions, and Clostridium beijerinckii TISTR 1461 was used as a butanol producer in an acetone-butanol–ethanol (ABE) fermentation. Sweet sorghum juice (SSJ) medium containing 60 g/L of total sugar supplemented with 1.27 g/L of (NH4)2SO4 was used as a butanol production (BP) medium. Arthrobacter sp. was inoculated into the BP medium in 1-L screw-capped bottles. After 2, 4, 6 and 12 h of Arthrobacter sp. cultivation at 30 °C, C. beijerinckii was transferred into the BP medium to start butanol production at 37 °C. The results showed that C. beijerinckii inoculation after 6 h of Arthrobacter sp. cultivation gave the highest butanol titer (PB) at 12.56 g/L, with a butanol yield (YB/S) and volumetric butanol productivity (QB) of 0.34 g/g and 0.23 g/L·h, respectively. These values are approximately 10–27% higher than those of the control experiment using a single culture of C. beijerinckii TISTR 1461 and oxygen-free nitrogen (OFN) gas flushing to create anaerobic conditions. Field emission scanning electron microscopic (FE-SEM) images of Clostridium cells, as well as protein and free amino nitrogen concentrations in the broth during butanol fermentation were also studied to confirm the results. The butanol fermentation was then carried out in a 5.6-L stirred-tank and a 1.2-L low-cost gas-lift bioreactor by the mixed cultures using the optimal time of Clostridium inoculation. The PB, YB/S and QB values obtained were not significantly different from those in the 1-L screw-capped bottles. Hence, Arthrobacter sp. can be used as a novel method to create anaerobic conditions instead of a traditional method employing OFN gas flushing. Using mixed cultures of Arthrobacter sp. BCC 72131 and C. beijerinckii TISTR 1461 is a practical method to produce butanol on a large-scale, both in complex and low-cost bioreactors.

Molecular biology: Fantastic toolkits to improve knowledge and application of acetic acid bacteria

Acetic acid bacteria (AAB) are a group of gram-negative, obligate aerobic bacteria within the Acetobacteraceae family of the alphaproteobacteria class, which are distributed in a wide variety of different natural sources that are rich in sugar and alcohols, as well as in several traditionally fermented foods. Their versatile capabilities are not limited to producing acetic acid and brewing vinegar, as their names suggest. They can also be used for fixing nitrogen, yielding pigments and exopolysaccharides (EPS), and most typically, producing a variety of aldehydes, ketones and other organic acids from the incomplete oxidation of the corresponding alcohols and/or sugars (also referred to as oxidative fermentation). In order to gain more insight into these organisms, molecular biology techniques have been extensively applied in almost all aspects of AAB research, including their identification and classification, acid resistance mechanisms, oxidative fermentation, EPS production, thermotolerance and so on. In this review, we mainly focus on the application of molecular biological technologies in the advancement of research into AAB while presenting the progress of the latest studies using these techniques.

Species composition and population level of the microbiota of the contents of the maxillary sinuses and oropharynx in patients with chronic purulent maxillary sinusitis with type 1 diabetes mellitus

Aim – to study the species composition and population level of the microbiota of the contents of the maxillary sinuses and oropharynx in patients with chronic purulent maxillary sinusitis (CPMS), which arose on the background of type 1 diabetes mellitus (DM).Material and methods. A microbiological examination of 97 samples of the contents of the maxillary sinus cavity was performed. The main group consisted of 50 patients with CPMS with type 1 diabetes aged 20-67 years (10 patients aged 20-31 years, 14 patients aged 31-45 years and 26 aged 45-67 years). Among patients of the main group, endocrinologists found in 39 patients the course of type 1 diabetes of moderate severity, in 11 - severe course. The control group consisted of 47 people of the same age, who during the last 6 months did not suffer from any diseases and considered themselves practically healthy.Results. The leading pathogens in CPMS in patients with type 1 (DM) are S. pneumoniae (34% of patients), H. influenzae (24%), M. catarrhalis (24%), S. aureus (10.0%), S. pyogenes (6.0%), E. coli Hly + (2.0%). It is established that the purulent-inflammatory process in the maxillary sinuses in patients with type 1 diabetes develops against the background of the formed dysbiosis of the oropharynx: 1st degree in 6.0%, 2nd degree - in 28% of patients and 3rd degree - in 66% of patients, which is characterized by a pronounced deficiency of indigenous obligate anaerobic and aerobic bacteria and contamination of the habitat with pathogenic and opportunistic pathogens and other microorganisms.Conclusions. The leading causative agents of chronic purulent maxillary sinusitis in patients with type 1 diabetes mellitus at the present stage are: S.pneumoniae (32.0%), H.influenzae (26.0%), M.catarrhalis (24.0%), S. pyogenes (10.0%), S. aureus (6.0%) and E. coli Hly + (2.0%). Patients with chronic purulent maxillary sinusitis, which developed on the background of type 1 diabetes mellitus, are eliminated from the habitat of bifidobacteria, lactococci and S. mutans, which are important for their multifunctional role in the microbiocenosis; the number of physiologically useful lactobacilli is significantly reduced by 2 orders of magnitude, salivary streptococci by 92.91%, S.viridans by 25.17%, S.sanguis by 86.17%, S.mitis by 45.33%, M.luteus-25.35%. Against this background, the number of opportunistic pathogens increases significantly by 84.59%, fusobacteria by 69.33%, pyogenic streptococcus - by 50.5%, hemophilic bacteria - by 55.71%, moraxella - by 74.01%, yeast-like fungi of the genus Candida - by 25.63%. Bacteria that contaminate the oropharynx and the contents of the cavities of the maxillary sinuses reach a high population level (from 4.33 ± 0.14 to 5.69 ± 0.09 lg KUO \ ml). In chronic purulent sinusitis in patients with type 1 diabetes mellitus in the contents of the oropharyngeal cavity are associations of autochthonous obligate and facultative opportunistic and allochthonous microorganisms, consisting of 3 types of microorganisms in 3 (6%) patients, out of 4 in 41 ( 82%) and out of 5 in 6 (12%) patients. Chronic purulent process in the maxillary sinus in patients with type 1 diabetes mellitus develops against the background of the formed dysbacteriosis / dysbiosis of the oropharynx I degree in 6.0%, II degree - in 28.0% of patients and III degree - in 66.0% of patients with chronic purulent maxillary sinusitis, characterized by elimination or severe deficiency of autochthonous obligate anaerobic and aerobic bacteria (bacteria of the genus Bifidobacterium, Lactobacillus, Streptococcus (S.salivarius, S.sanguis, S.mitis, S.mutans, L.lactis, M.luteus) biotope contamination by pathogenic and conditionally pathogenic S.pneumoniae, S.pyogenes, H.influenzae, M.catarrhalis, E.coli, E.coli Hly+, Enterobacter freundii., Klebsiella oxytoca, S.aureus and others.

Complete Genome Analysis of Undecylprodigiosin Pigment Biosynthesizing Marine Streptomyces Species Displaying Potential Bioactive Applications

Marine Streptomyces species are underexplored for their pigment molecules and genes. In this study, we report the genome of the undecylprodigiosin biosynthesizing gene cluster carrying Streptomyces sp. strain BSE6.1, displaying antioxidant, antimicrobial, and staining properties. This Gram-positive obligate aerobic bacterium was isolated from the coastal sediment of the Andaman and Nicobar Islands, India. Pink to reddish pigmented colonies with whitish powdery spores on both agar and broth media are the important morphological characteristics of this bacterium. Growth tolerance to NaCl concentrations was 2 to 7%. The assembled genome of Streptomyces sp. BSE6.1 contains one linear chromosome 8.02 Mb in length with 7157 protein-coding genes, 82 tRNAs, 3 rRNAs and at least 11 gene clusters related to the synthesis of various secondary metabolites, including undecylprodigiosin. This strain carries type I, type II, and type III polyketide synthases (PKS) genes. Type I PKS gene cluster is involved in the biosynthesis of red pigment undecylprodigiosin of BSE6.1, similar to the one found in the S. coelicolor A3(2). This red pigment was reported to have various applications in the food and pharmaceutical industries. The genome of Streptomyces sp. BSE6.1 was submitted to NCBI with a BioProject ID of PRJNA514840 (Sequence Read Archive ID: SRR10849367 and Genome accession ID: CP085300).

Efektivitas Pupuk Cair Pseudomonas fluorescens Agensia Pengendali Hayati Terhadap Penyakit Mosaik Tanaman Kakao

Cocoa is a strategic commodity for plantation in Indonesia. However, pest and disease infections are inevitably common constrains for the cocoa cultivators. Cocoa mosaic disease is one of disease which is cause cocoa trees suffering. Pseudomonas fluorescens are obligate aerobic bacteria that are very valuable for agricultural technology. The bacteria also protects plants from pathogens infection by producing secondary metabolites that kill bacteria and other fungi. The bacteria can used as safe and environmentally friendly biological control agents. This study aims to determine P. fluorescens liquid fertilizer formulation and its effectiveness in suppressing mosaic disease in cocoa plants. The research method was carried out by making a liquid formula from P. fluorescens and then applying it to cocoa plants that were attacked by mosaic disease. Bacterian isolates grown in conch broth medium were incubated for 3 days. Then the fertilizer formula was applied to mosaic symptomatic cocoa plants with fertilizer concentrations of 25%, 50% and 75% compared to spraying using chemical insecticides. The results showed that the liquid formula concentration of 75% can suppress the most effective mosaic symptoms and the optimal growth of cocoa plants for 7 treatments.

Bdellovibrio bacteriovorus Hydrolyses its Prey DNA using the Dctpase Activity of Bd2220

NUDIX hydrolases, phosphoanhydrases conserved across species, catalyze the hydrolysis of various nucleoside diphosphates linked to different moieties, X (NUDIX). Bdellovibrio is a gram-negative, obligate aerobic bacterium that predates other gram-negative bacteria by invading their periplasm and hydrolyzing and feeding on the biopolymers of the prey to synthesize its own DNA. Often found in river waters and soil, bdellovibrio also exists in the mammalian digestive track and has a bi-phasic, short lifecycle that includes a free-living, predatory and an alternating intra-periplasmic growth phases involving the formation of a prey scavenging bdelloplast.

FORMULASI PUPUK CAIR Pseudomonas fluorescens SEBAGAI AGENSIA PENGENDALI HAYATI PENYAKIT MOSAIK TANAMAN KAKAO

Cocoa is a strategic commodity for plantation in Indonesia. However, pest and disease infections are inevitably common constrains for the cocoa cultivators. Cocoa mosaic disease is one of disease which is cause cocoa trees suffering. Pseudomonas fluorescens are obligate aerobic bacteria that are very valuable for agricultural technology. The bacteria also protect plants from pathogens infection by producing secondary metabolites that kill bacteria and other fungi. The bacteria can use as safe and environmentally friendly biological control agents. This study aims to determine P. fluorescens liquid fertilizer formulation and its effectiveness in suppressing mosaic disease in cocoa plants. The research method was carried out by making a liquid formula from P. fluorescens and then applying it to cocoa plants that were attacked by mosaic disease. Bacteria isolates grown in conch broth medium were incubated for 3 days. Then the fertilizer formula was applied to mosaic symptomatic cocoa plants with fertilizer concentrations of 25%, 50% and 75% compared to spraying using chemical insecticides. The results showed that the liquid formula concentration of 75% can suppress the most effective mosaic symptoms and the optimal growth of cocoa plants for 7 treatments.. Keywords: Cocoa, Formulation, mosaic disease, Pseudomonas fluorescens

Roseobacter cerasinus sp. nov., isolated from a fish farm.

An obligate aerobic and bacteriochlorophyll a-containing bacterium, designated strain AI77T, was isolated from a fish farm in Uwa Sea, Japan. Cells were Gram-stain-negative, coccoid- to oval-shaped, and showed no motility. Phylogenetic analysis based on the 16S rRNA gene sequences revealed that strain AI77T is a member of the genus Roseobacter and closely related to Roseobacter ponti MM-7T (97.8 %), Roseobacter denitrificans OCh 114T (97.3 %) and Roseobacter litoralis OCh 149T (97.3 %). The G+C content of strain AI77T was 61.0 mol%. The average amino acid identity values of the genome in strain AI77T with those in R. denitrificans OCh 114T and R. litoralis OCh 149T were 73.26 % (SD 16.46) and 72.63 % (SD 16.76), respectively. The digital DNA-DNA hybridization values of strain AI77T with the type strains R. denitrificans OCh 114T and R. litoralis OCh 149T were 18.70 and 18.50 %, respectively. The dominant fatty acids (>10 % of total fatty acids) of AI77T were summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c) and saturated fatty acid C16 : 0. The sole respiratory quinone was ubiquinone-10. The predominant polar lipids were phosphatidylcholine, phosphatidylglycerol and diphosphatidylglycerol. Based on the genetic and phenotypic data obtained herein, we conclude that strain AI77T represents a new species of the genus Roseobacter, for which we propose the name Roseobacter cerasinus sp. nov.; the type strain is AI77T (=DSM 110091T=NBRC 114115T).

Complete genome of Polaromonas vacuolata KCTC 22033T isolated from beneath Antarctic Sea ice.

Polaromonas vacuolata KCTC 22033T is an obligate aerobic, Gram-negative, psychrophilic and rod-shaped bacterium isolated from beneath the sea ice off the coast of the Palmer Peninsula, Anvers Islands, Antarctica. P. vacuolata is the type species of Polaromonas genus and the first example of gas vacuolate Betaproteobacteria isolated from marine habitats. Here, we report a complete genome of P. vacuolata KCTC 22033T, which consists of 3,837,686bp (G+C content of 52.07%) with a single chromosome, 3461 protein-coding genes, 56 tRNAs and 6 rRNA operons. Genomic analysis revealed the presence of genes involved in bacterial adaptation under saline conditions, cold adaptation via the production of gas vesicles and cell adhesion proteins, and a photoheterotrophic lifestyle when challenged by starvation. Intriguingly, several of these genes were likely acquired from species outside the Polaromonas genus. The genomic information therefore describes the unique evolution and adaptation of P. vacuolata to its extraordinary habitat, i.e., beneath the Antarctic sea ice.

Bioconversion of 5-Hydroxymethylfurfural (HMF) to 2,5-Furandicarboxylic Acid (FDCA) by a Native Obligate Aerobic Bacterium, Acinetobacter calcoaceticus NL14.

2,5-Furandicarboxylic acid (FDCA), one of the top biomass-based platform chemical, is highly promising for resins and polymers, and it can be prepared from the bio-oxidation of hydroxymethyl furfural (HMF), which can be obtained mainly from lignocellulosic glucose that has a high production potential from not edible biomass.A native strain, Acinetobacter calcoaceticus NL14, that could convert HMF into FDCA is used for combining degradation and fermentation by consolidated bioprocessing (CBP). In this study, it was observed that the initial HMF concentration and pH neutralizer played important roles in the bioconversion of HMF, 5g/L of HMF could be converted by 100% within 48h with 0.5g/L sodium carbonate (Na2CO3) with the production of 0.31g/L FDCA. Extra glucose and hydrogen peroxide (H2O2) addition could further promote the production of FDCA to 0.54g/L with 100% HMF conversion and a higher conversion rate. This report could provide a potential native bacterium for furan chemicals bioconversion and bioelimination, especially for FDCA bioproduction.

Development of a novel selective medium for the isolation and enumeration of acetic acid bacteria from various foods

Acetic acid bacteria (AAB) are gram-negative, obligate aerobic bacteria that produce acetic acid from alcohols or sugars. AAB are ubiquitous and found in many food products, including vinegar and wine. Owing to the lack of a suitable selective culture medium and the fastidious nature of AAB in food samples, ecological studies have been fundamentally limited for decades. Here, we developed a novel selective medium (AAB-selective agar; ABS) for AAB from food samples and evaluated its performance in comparison with glucose-yeast extract-calcium carbonate agar (GYC). In inclusivity tests, 16 species of AAB showed good growth on both ABS and GYC. Remarkably, the growth of 21 non-AAB strains was inhibited on ABS but not on GYC, suggesting the high exclusivity of the novel selective medium (p < 0.05). In artificial AAB-positive food samples, including wine, vinegar, yogurt, fruit, and kimchi, ABS provided better visual differentiation of AAB colonies, showing green colonies with a yellow halo surrounded by no competing colonies. Moreover, in ABS, a significantly greater number of AAB colonies were recovered from yogurts, fruits, and kimchi (Acetobacter aceti ATCC 15973 in yogurt, 4.24 ± 0.17 vs. 3.80 ± 0.14; Gluconobacter oxydans ATCC 15163 in fruit, 4.87 ± 0.07 vs. 4.53 ± 0.15; Gluconacetobacter hansenii ATCC 35959 in kimchi, 4.25 ± 0.14 vs. 3.85 ± 0.12; p < 0.05). Finally, a total of five novel AAB strains were isolated from 10 vinegar and 10 kimchi samples using ABS, while unsuccessful using GYC, demonstrating the superior performance of ABS in isolating new AAB strains or detecting AAB contamination.

Electrodialytic bioproduction of xylonic acid in a bioreactor of supplied-oxygen intensification by using immobilized whole-cell Gluconobacter oxydans as biocatalyst

Immobilized whole-cell fermentation has been proven to be an effective method to improve the performance and cost-effectiveness of Gluconobacter oxydans ATCC 621. In the bio-oxidation of xylose to xylonic acid, the oxygen supply through the immobilized beads is a well-known factor that limits the biocatalytic performance of Gluconobacter oxydans as obligate aerobic bacteria. The activity of immobilized cells could be efficiently improved by execution of pressurized pure oxygen supply strategy. Subsequently, in order to further enhance the production efficiency of xylonic acid and reduce end-product inhibition, online-electrodialysis was employed. Finally, a design of pressurized oxygen supply bioreactor combining with online-electrodialysis was put forward for implementing successive production of xylonic acid. The central features of this a highly integrated design are feasible and thus might enable cost-competitive bacterial xylonic acid production.

Holocene paleodepositional changes reflected in the sedimentary microbiome of the Black Sea.

Subsurface microbial communities are generally thought to be structured through in situ environmental conditions such as the availability of electron acceptors and donors and porosity, but recent studies suggest that the vertical distribution of a subset of subseafloor microbial taxa, which were present at the time of deposition, were selected by the paleodepositional environment. However, additional highly resolved temporal records of subsurface microbiomes and paired paleoenvironmental reconstructions are needed to justify this claim. Here, we performed a highly resolved shotgun metagenomics survey to study the taxonomic and functional diversity of the subsurface microbiome in Holocene sediments underlying the permanently stratified and anoxic Black Sea. Obligate aerobic bacteria made the largest contribution to the observed shifts in microbial communities associated with known Holocene climate stages and transitions. This suggests that the aerobic fraction of the subseafloor microbiome was seeded from the water column and did not undergo post-depositional selection. In contrast, obligate and facultative anaerobic bacteria showed the most significant response to the establishment of modern-day environmental conditions 5.2ka ago that led to a major shift in planktonic communities and in the type of sequestered organic matter available for microbial degradation. No significant shift in the subseafloor microbiome was observed as a result of environmental changes that occurred shortly after the marine reconnection, 9ka ago. This supports the general view that the marine reconnection was a gradual process. We conclude that a high-resolution analysis of downcore changes in the subseafloor microbiome can provide detailed insights into paleoenvironmental conditions and biogeochemical processes that occurred at the time of deposition.

Application of deoxygenation-aeration cycling to control the predatory bacterium Vampirovibrio chlorellavorus in Chlorella sorokiniana cultures

A previously untested approach was evaluated to enable management of the predatory bacterium, Vampirovibrio chlorellavorus, a pathogen of Chlorella sorokiniana, in suspension cultures grown in a laboratory test reactor. Because V. chlorellavorus is an obligate aerobic bacterium, whereas C. sorokiniana grows under aerobic and anaerobic conditions, deoxygenation of the culture was expected to be detrimental to the pathogen, but not to the algal host. The effect of deoxygenation on the uninfected (healthy) C. sorokiniana suspension cells, compared to the C. sorokiniana-V. chlorellavorus co-culture, was studied in relation to biomass, dissolved oxygen, ratio of C. sorokiniana to V. chlorellavorus DNA, and visual and light microscopic observations. Preliminary experiments were conducted to test the effects of different deoxygenation-aeration cycling regimes on performance of V. chlorellavorus-free C. sorokiniana cultures. To an aerobic culture, pure nitrogen gas was introduced to create anoxic conditions, followed by the injection of ambient air to re-establish an aerobic environment. Under this repeated cycling regime, C. sorokiniana was shown to tolerate the anoxic conditions for extended timespans that ranged from 2 to 8 h over a 5-day test period. The analogous aerobic-anoxic cycling with the C. sorokiniana-V. chlorellavorus co-cultures resulted in ‘near-normal’ growth cycle and harvestable biomass, whereas the continuously-aerated (aerobic) co-cultures that were grown without the deoxygenation step in the cycle collapsed in 3 days. Visual and light microscopic observations revealed intact C. sorokiniana cells were present in the deoxygenated cultures, compared to the aerobically-grown, brown-colored algal cultures consisting of collapsed cells. Quantitative polymerase chain reaction analysis showed continuous increases in the ratio of V. chlorellavorus (16S rDNA) to C. sorokiniana (18S rDNA) DNA in the aerated co-cultures, with greater increases during dark periods, while the pathogen-to-host DNA ratio in the deoxygenated co-cultures was relatively low and algal cells did not collapse, as would be expected following pathogen attack.

Current taxonomy of Rhodococcus species and their role in infections.

Rhodococcus is a genus of obligate aerobic, Gram-positive, partially acid-fast, catalase-positive, non-motile, and none-endospore bacteria. The genus Rhodococcus was first introduced by Zopf. This bacterium can be isolated from various sources of the environment and can grow well in non-selective medium. A large number of phenotypic characterizations are used to compare different species of the genus Rhodococcus, and these tests are not suitable for accurate identification at the genus and species level. Among nucleic acid-based methods, the most powerful target gene for revealing reliable phylogenetic relationships is 16S ribosomal RNA gene (16S rRNA gene) sequence analysis, but this gene is unable to differentiation some of Rhodococcus species. To date, whole genome sequencing analysis has solved taxonomic complexities in this genus. Rhodococcus equi is the major cause of foal pneumonia, and its implication in human health is related to cases in immunocompromised patients. Macrolide family together with rifampicin is one of the most effective antibiotic agents for treatment rhodococcal infections.

Novel mechanisms of selenate and selenite reduction in the obligate aerobic bacterium Comamonas testosteroni S44

Selenium oxyanion reduction is an effective detoxification or/and assimilation processes in organisms, but little is known the mechanisms in aerobic bacteria. Aerobic Comamonas testosteroni S44 reduces Se(VI)/Se(IV) to less-toxic elemental selenium nanoparticles (SeNPs). For Se(VI) reduction, sulfate and Se(VI) reduction displayed a competitive relationship. When essential sulfate reducing genes were respectively disrupted, Se(VI) was not reduced to red-colored SeNPs. Consequently, Se(VI) reduction was catalyzed by enzymes of the sulfate reducing pathway. For Se(IV) reduction, one of the potential periplasm molybdenum oxidoreductase named SerT was screened and further used to analyze Se(IV) reduction. Compared to the wild type and the complemented mutant strain, the ability of Se(IV) reduction was reduced 75% in the deletion mutant ΔserT. Moreover, the Se(IV) reduction rate was significantly enhanced when the gene serT was overexpressed in Escherichia coli W3110. In addition, Se(IV) was reduced to SeNPs by the purified SerT with the presence of NADPH as the electron donor in vitro, showing a Vmax of 61 nmol/min·mg and a Km of 180 μmol/L. A model of Se(VI)/Se(IV) reduction was generated in aerobic C. testosteroni S44. This work provides new insights into the molecular mechanisms of Se(VI)/Se(IV) reduction activities in aerobic bacteria.