Furfural biotransformation in Acinetobacter baylyi ADP1 and Acinetobacter schindleri ACE.

OBJECTIVES: To determine furfural biotransformation capabilities of Acinetobacter baylyi ADP1 and Acinetobacter schindleri ACE. RESULTS: Acinetobacter baylyi ADP1 and A. schindleri ACE could not use furfural as sole carbon source but when acetate was used as substrate, ADP1 and ACE biotransformed 1 g furfural/l in 5 and 9 h, respectively. In both cases, the product of this biotransformation was difurfuryl-ether as shown by FT-IR and 1H and 13C NMR spectroscopy. The presence of furfural decreased the specific growth rate in acetate by 27% in ADP1 and 53% in ACE. For both strains, the MIC of furfural was 1.25 g/l. Nonetheless, ADP1 biotransformed 2 g furfural/l at a rate of 1 g/l/h in the stationary phase of growth. A transcriptional analysis of possible dehydrogenases involved in this biotransformation, identified that the areB and frmA genes were highly overexpressed after the exposure of ADP1 to furfural. The products of these genes are a benzyl-alcohol dehydrogenase and an alcohol dehydrogenase. CONCLUSIONS: Acinetobacter baylyi ADP1 is a candidate for the biological detoxification of furfural, a fermentation inhibitor present in lignocellulosic hydrolysates, with the possible direct involvement of the AreB and FrmA enzymes in the process.

Nitrate removal performances of a new aerobic denitrifier, Acinetobacter haemolyticus ZYL, isolated from domestic wastewater.

A new aerobic denitrifying bacterium ZYL was isolated from domestic wastewater sludge and identified as Acinetobacter haemolyticus (similarity 99%) by the 16S rDNA sequencing analysis. The strain could use nitrate, nitrite and ammonium as the sole N-source for growth with a final product of N2, demonstrating its good abilities for aerobic denitrification and heterotrophic nitrification. Single-factor experiment results showed that the effective removal of nitrate by strain ZYL occurred with carbon source sodium succinate, C/N 16-24, pH 5-9, temperature 20-40 °C, DO ≥ 4.84 mg/L. Ammonium was preferentially used by strain ZYL with nitrate and ammonium as the mixed nitrogen sources. According to nitrogen utilization, nitrogen balance analysis, enzyme assay and denitrifying gene amplification, nitrate was assimilated directly by the isolate for cell synthesis and also converted into N2 through aerobic denitrification. All these make strain ZYL an ideal choice for treating nitrogen-containing wastewater.

Metabolic Profiling to Determine Bactericidal or Bacteriostatic Effects of New Natural Products using Isothermal Microcalorimetry.

Due to the global threat of rising antimicrobial resistance, novel antibiotics are urgently needed. We investigate natural products from Myxobacteria as an innovative source of such new compounds. One bottleneck in the process is typically the elucidation of their mode-of-action. We recently established isothermal microcalorimetry as part of a routine profiling pipeline. This technology allows for investigating the effect of antibiotic exposure on the total bacterial metabolic response, including processes that are decoupled from biomass formation. Importantly, bacteriostatic and bactericidal effects are easily distinguishable without any user intervention during the measurements. However, isothermal microcalorimetry is a rather new approach and applying this method to different bacterial species usually requires pre-evaluation of suitable measurement conditions. There are some reference thermograms available of certain bacteria, greatly facilitating interpretation of results. As the pool of reference data is steadily growing, we expect the methodology to have increasing impact in the future and expect it to allow for in-depth fingerprint analyses enabling the differentiation of antibiotic classes.

Antimicrobial activity as a potential factor influencing the predominance of Bacillus subtilis within the constitutive microflora of a whey reverse osmosis membrane biofilm.

Current cleaning and sanitation protocols may not be adequately effective in cleaning separation membranes and can result in the formation of resilient multispecies biofilms. The matured biofilms may result in a bacterial predominance with resilient strains on membranes with a prolonged use. In our previous study, we isolated organisms such as Bacillus subtilis, Bacillus licheniformis, Exiguobacterium aurantiacum, and Acinetobacter radioresistens from an 18-mo-old reverse osmosis membrane. The competitive exclusion studies revealed the predominance of B. subtilis within the membrane biofilm microflora. This study investigated the antimicrobial activity of the B. subtilis isolate as a potential cause of its predominance. The culture isolate was propagated in tryptic soy broth at 37°C, and microfiltered to prepare cell-free extracts (CFE) at 8-, 10-, 12-, 14-, 16-, and 18-h intervals. The CFE were freeze-dried and suspended in minimum quantities of HPLC-grade water to prepare concentrated solutions. The antimicrobial activities of CFE were tested using the agar-well assay against the biofilm constitutive microflora. The experiments were conducted in triplicates and means were compared for significant differences using a general linear mixed model procedure. The results indicated the highest antimicrobial activity of 12-h CFE of B. subtilis against other constitutive microflora such as Exiguobacterium sp., E. auranticum, and A. radioresistens, with average inhibition zone sizes of 16.5 ± 0.00, 16.25 ± 0.66, and 20.6 ± 0.00 mm, respectively. Upon treatment with proteinase K, the CFE completely lost its antimicrobial activity, establishing it to be a proteinaceous compound. The AA profiling revealed the total crude protein in CFE to be 51% (wt/wt), with its major constituent as glutamic acid (11.30% wt/wt). The freeze-dried CFE was thermally stable on exposure to the common temperature used for sanitizer applications (23.8°C for 5 and 10 min) and over a pH range of 3.0 to 6.3. The study helped us understand the role of the antimicrobial compound produced by B. subtilis as a potential cause of its predominance within the biofilm constitutive microflora.

Growth Kinetics and Spoilage Potential of Co-culturing Acinetobacter johnsonii and Pseudomonas fluorescens from Bigeye Tuna (Thunnus obesus) During Refrigerated Storage.

A. johnsonii and P. fluorescens are the well-known specific spoilage organisms in aquatic products and the study of the interactions between A. johnsonii and P. fluorescens are limited. This study aims to evaluate the growth kinetics, spoilage potential and interactions of A. johnsonii and P. fluorescens isolated from spoiled bigeye tuna (Thunnus obesus) by inoculating into sterile fish slices and stored at 4 °C for 6 days. The growth kinetics of A. johnsonii and P. fluorescens were fitted with Baranyi and Roberts model. The chemical indexes (total volatile base nitrogen (TVB-N), trimethylamine (TMA), pH, proteolytic activity and protein content) of each inoculated block of bigeye tuna were increased during refrigerated storage. Moreover, the higher contents of chemical indexes were observed in co-culture with A. johnsonii and P. fluorescens compared with single culture of A. johnsonii and P. fluorescens. In addition, atomic force microscopy (AFM) observation of co-culturing A. johnsonii and P. fluorescens inoculation into sterile fish slices revealed damage of myofibrillar protein structures and the protein degradation. Based on these parameters, a rapid method to evaluate spoilage potential of A. johnsonii and P. fluorescens was positively correlated with TVB-N value, TMA value and pH value (P < 0.05) by the correlation coefficient. Consequently, spoilage potential of microorganisms became stronger evaluated in a mixed culture than single culture. This paper provides insight for a detection method of interactions of A. johnsonii and P. fluorescens during refrigerated storage.

Rapid and assured genetic engineering methods applied to Acinetobacter baylyi ADP1 genome streamlining.

One goal of synthetic biology is to improve the efficiency and predictability of living cells by removing extraneous genes from their genomes. We demonstrate improved methods for engineering the genome of the metabolically versatile and naturally transformable bacterium Acinetobacter baylyi ADP1 and apply them to a genome streamlining project. In Golden Transformation, linear DNA fragments constructed by Golden Gate Assembly are directly added to cells to create targeted deletions, edits, or additions to the chromosome. We tested the dispensability of 55 regions of the ADP1 chromosome using Golden Transformation. The 18 successful multiple-gene deletions ranged in size from 21 to 183 kb and collectively accounted for 23.4% of its genome. The success of each multiple-gene deletion attempt could only be partially predicted on the basis of an existing collection of viable ADP1 single-gene deletion strains and a new transposon insertion sequencing (Tn-Seq) dataset that we generated. We further show that ADP1's native CRISPR/Cas locus is active and can be retargeted using Golden Transformation. We reprogrammed it to create a CRISPR-Lock, which validates that a gene has been successfully removed from the chromosome and prevents it from being reacquired. These methods can be used together to implement combinatorial routes to further genome streamlining and for more rapid and assured metabolic engineering of this versatile chassis organism.

The mismatch repair system (mutS and mutL) in Acinetobacter baylyi ADP1.

BACKGROUND: Acinetobacter baylyi ADP1 is an ideal bacterial strain for high-throughput genetic analysis as the bacterium is naturally transformable. Thus, ADP1 can be used to investigate DNA mismatch repair, a mechanism for repairing mismatched bases. We used the mutS deletion mutant (XH439) and mutL deletion mutant (XH440), and constructed a mutS mutL double deletion mutant (XH441) to investigate the role of the mismatch repair system in A. baylyi. RESULTS: We determined the survival rates after UV irradiation and measured the mutation frequencies, rates and spectra of wild-type ADP1 and mutSL mutant via rifampin resistance assay (RifR assay) and experimental evolution. In addition, transformation efficiencies of genomic DNA in ADP1 and its three mutants were determined. Lastly, the relative growth rates of the wild type strain, three constructed deletion mutants, as well as the rifampin resistant mutants obtained from RifR assays, were measured. All three mutants had higher survival rates after UV irradiation than wild type, especially the double deletion mutant. Three mutants showed higher mutation frequencies than ADP1 and favored transition mutations in RifR assay. All three mutants showed increased mutation rates in the experimental evolution. However, only XH439 and XH441 had higher mutation rates than the wild type strain in RifR assay. XH441 showed higher transformation efficiency than XH438 when donor DNA harbored transition mutations. All three mutants showed higher growth rates than wild-type, and these four strains displayed higher growth rates than almost all their rpoB mutants. The growth rate results showed different amino acid mutations in rpoB resulted in different extents of reduction in the fitness of rifampin resistant mutants. However, the fitness cost brought by the same mutation did not vary with strain background. CONCLUSIONS: We demonstrated that inactivation of both mutS and mutL increased the mutation rates and frequencies in A. baylyi, which would contribute to the evolution and acquirement of rifampicin resistance. The mutS deletion is also implicated in increased mutation rates and frequencies, suggesting that MutL may be activated even in the absence of mutS. The correlation between fitness cost and rifampin resistance mutations in A. baylyi is firstly established.

Flower-like patterns in multi-species bacterial colonies.

Diverse interactions among species within bacterial colonies lead to intricate spatiotemporal dynamics, which can affect their growth and survival. Here, we describe the emergence of complex structures in a colony grown from mixtures of motile and non-motile bacterial species on a soft agar surface. Time-lapse imaging shows that non-motile bacteria 'hitchhike' on the motile bacteria as the latter migrate outward. The non-motile bacteria accumulate at the boundary of the colony and trigger an instability that leaves behind striking flower-like patterns. The mechanism of the front instability governing this pattern formation is elucidated by a mathematical model for the frictional motion of the colony interface, with friction depending on the local concentration of the non-motile species. A more elaborate two-dimensional phase-field model that explicitly accounts for the interplay between growth, mechanical stress from the motile species, and friction provided by the non-motile species, fully reproduces the observed flower-like patterns.

Communities of bacteria and other microbes live in every ecosystem on Earth, including in soil, in hydrothermal vents, on the surface of plants and in the human gut. They often attach to solid surfaces and form dense colonies called biofilms. Most biofilms found in nature are comprised of many different species of bacteria. How the bacteria interact shapes the internal structures of these communities. Many previous studies have focused on the molecules that bacteria use to relate to each other, for example, some bacteria exchange nutrients or release toxins that are harmful to their neighbors. However, it is less clear how direct physical contacts between bacteria affect the whole community. Escherichia coli is a rod-shaped bacterium that is a good swimmer, but has a hard time moving on solid surfaces. Therefore, when a droplet of liquid containing these bacteria is placed in a Petri dish containing a jelly-like substance called agar, the droplet barely expands over a 24-hour period. On the other hand, a droplet containing another rod-shaped bacterium known as Acinetobacter baylyi expands rapidly on agar because these bacteria are able to crawl using microscopic "legs" called pili. Here, Xiong et al. set out to investigate how a colony containing both E. coli and A. baylyi developed on a solid surface. The experiments showed that when a droplet of liquid containing both species was placed on agar, both species grew and spread rapidly, as if the E. coli hitchhiked on the highly motile A. baylyi cells. Furthermore, the growing colony developed a complex flower-like shape. Xiong et al. developed mathematical models that took into account how quickly each species generally grows, their ability to move, the friction between cells and the agar, and other physical properties. The models predicted that the E. coli cells that accumulate at the expanding boundary of the colony make the boundary unstable, leading to the flower-like patterns. Further analysis suggested that similar patterns may form in other situations when motile and non-motile species of bacteria are together. These findings may help us understand the origins of the complex structures observed in many naturally occurring communities of bacteria.

Effects of phytic acid and lysozyme on microbial composition and quality of grass carp (Ctenopharyngodon idellus) fillets stored at 4 °C.

This study investigated the effect of phytic acid and lysozyme on the microbial composition and quality of grass carp (Ctenopharyngodon idellus) fillets stored at 4 °C. The control, 0.5 mg/mL lysozyme-treated fillets (T1), 0.5 mg/mL phytic acid-treated fillets (T2) and 0.25 mg/mL lysozyme + 0.25 mg/mL phytic acid-treated fillets (T3) were evaluated based on sensory assessment, biogenic amines, ATP-related compounds, total volatile basic nitrogen (TVB-N), and total viable counts (TVC). Changes in microbial composition were analyzed using high-throughput sequencing. Results showed that phytic acid and lysozyme treatment delayed the decrease in sensory scores, reduced the rate of degradation of IMP to Hx, inhibited the growth of microorganisms, and attenuated the increase in TVB-N and putrescine. Phytic acid exhibited better preservation effects than lysozyme and their combination was more effective than using either alone. High-throughput sequencing showed that Acinetobacter and Kocuria were the predominant bacteria in fresh grass carp, but Pseudomonas rose rapidly with storage time; Pseudomonas, Shewanella, and Aeromonas constituted the main spoilage bacteria of grass carp fillets. Lysozyme treatment significantly reduced the proportion of Shewanella and Acinetobacter, and phytic acid and the combination of phytic acid and lysozyme significantly reduced the proportion of Pseudomonas in spoiled grass carp fillets.

Phragmites australis in combination with hydrocarbons degrading bacteria is a suitable option for remediation of diesel-contaminated water in floating wetlands.

The presence of diesel in the water could reduce the growth of plant and thus phytoremediation efficacy. The toxicity of diesel to plant is commonly explained; because of hydrocarbons in diesel accumulate in various parts of plants, where they disrupt the plant cell especially, the epidemis, leaves, stem and roots of the plant. This study investigated the effect of bacterial augmentation in floating treatment wetlands (FTWs) on remediation of diesel oil contaminated water. A helophytic plant, Phragmites australis (P. australis), was vegetated on a floating mat to establish FTWs for the remediation of diesel (1%, w/v) contaminated water. The FTWs was inoculated with three bacterial strains (Acinetobacter sp. BRRH61, Bacillus megaterium RGR14 and Acinetobacter iwoffii AKR1), possessing hydrocarbon degradation and plant growth-enhancing capabilities. It was observed that the FTWs efficiently removed hydrocarbons from water, and bacterial inoculation further enhanced its hydrocarbons degradation efficacy. Diesel contaminated water samples collected after fifteen days of time interval for three months and were analyzed for pollution parameters. The maximum reduction in hydrocarbons (95.8%), chemical oxygen demand (98.6%), biochemical oxygen demand (97.7%), total organic carbon (95.2%), phenol (98.9%) and toxicity was examined when both plant and bacteria were employed in combination. Likewise, an increase in plant growth was seen in the presence of bacteria. The inoculated bacteria showed persistence in the water, root and shoot of P. australis. The study concluded that the augmentation of hydrocarbons degrading bacteria in FTWs is a better option for treatment of diesel polluted water.

The performance and mechanism of simultaneous removal of fluoride, calcium, and nitrate by calcium precipitating strain Acinetobacter sp. H12.

A calcium precipitating and denitrifying bacterium H12 was used to investigate the F- removal performance and mechanism. The results showed that the strain H12 reduced 85.24% (0.036 mg·L-1·h-1) of F-, 62.43% (0.94 mg·L-1·h-1) of Ca2+, and approximately 100% of NO3- over 120 h in continuous determination experiments. The response surface methodology analysis demonstrated that the maximum removal efficiency of F- was 88.98% (0.062 mg·L-1·h-1) within 72 h under the following conditions: the initial Ca2+ concentration of 250.00 mg·L-1, pH of 7.50, and the initial C4H4Na2O4·6H2O concentration of 800.00 mg·L-1. The scanning electron microscopy images, the X-ray photoelectron spectroscopy, and X-ray diffraction results suggested the following removal mechanism of F-: (1) the bacteria, as the nucleation site, were encapsulated by bioprecipitation to form biological crystal seeds; (2) Biological crystal seeds adsorbed F- to form Ca5(PO4)3F and CaF2; (3) Under the induction of bacteria, calcium, fluoride and phosphate coprecipitated to form Ca5(PO4)3F and CaF2. In addition, the gas chromatography data indicated that F- had little or no effect on the gas composition during denitrification, and the fluorescence spectroscopy analysis also proved that the extracellular polymeric substance (protein) is the site of bioprecipitation nucleation.

Dithiin diisoimides: Synthesis and their antimicrobial studies.

Sixteen derivatives of dithiin diisoimide 2a-2p have been synthesized and screened for antibacterial and antifungal activity. Compounds 2a-2g and 2i-2p are almost same or more active than gentamicine against Acinetobacter. Whereby compound 2,6-didodecyl-1H,5H-pyrrolo[3',4',5,6][1,4]dithiino[2,3-c]pyrrole-1,3,5,7(2H,6H)-tetrone (2d) having zone of inhibition 20 mm against Acinetobacter is the most potent among all these compounds and can be used as lead compound for the treatment of Acinetobacter infection.

Isolation, characterization and growth kinetics of phenol hyper-tolerant bacteria from sewage-fed aquaculture system.

Pollution of aquatic resources is increasing day-by-day, and phenolic compounds are common pollutants negatively impacting aquatic biodiversity and production. This study aimed at isolation of phenol hyper-tolerant bacteria from polluted aquaculture resource so that they might be useful in aquaculture systems. Four phenol hyper-tolerant bacterial strains were isolated from sewage fed East Kolkata Wetlands, a Ramsar site. By 16S rDNA sequence, cell morphology and biochemical characteristics the strains PDB2, PDB13, PDB16, and PDB26 were identified as Acinetobacter sp., Acinetobacter junii, Pseudomonas citronellolis, and Bacillus cereus, respectively. Pseudomonas citronellolis strain PDB16, described in this study, is possibly the first report of phenol hyper-tolerant strain in this species. All the four strains degraded 600 mg L-1 phenol within 5 days and expressed catechol 1,2-dioxygenase but lacked catechol 2,3-dioxygenase enzyme suggesting that the bacteria used the ortho-cleavage pathway for phenol degradation. In growth kinetic study Edwards and Aiba model, rather than the most popular Haldane model, gave the best fit indicating behavioral divergence of these strains with those from petroleum contaminated environments. The phenol degrading bacteria isolated from a polluted sewage fed aquaculture system might be useful in degradation and remediation of polluted aquaculture resources as well as inland open waters.

Enhanced Population Control in a Synthetic Bacterial Consortium by Interconnected Carbon Cross-Feeding.

Engineered microbial consortia can provide several advantages over monocultures in terms of utilization of mixed substrates, resistance to perturbations, and division of labor in complex tasks. However, maintaining stability, reproducibility, and control over population levels in variable conditions can be challenging in multispecies cultures. In our study, we modeled and constructed a synthetic symbiotic consortium with a genetically encoded carbon cross-feeding system. The system is based on strains of Escherichia coli and Acinetobacter baylyi ADP1, both engineered to be incapable of growing on glucose on their own. In a culture supplemented with glucose as the sole carbon source, growth of the two strains is afforded by the exchange of gluconate and acetate, resulting in inherent control over carbon availability and population balance. We investigated the system robustness in terms of stability and population control under different inoculation ratios, substrate concentrations, and cultivation scales, both experimentally and by modeling. To illustrate how the system might facilitate division of genetic circuits among synthetic microbial consortia, a green fluorescent protein sensitive to pH and a slowly maturing red fluorescent protein were expressed in the consortium as measures of a circuit's susceptibility to external and internal variability, respectively. The symbiotic consortium maintained stable and linear growth and circuit performance regardless of the initial substrate concentration or inoculation ratio. The developed cross-feeding system provides simple and reliable means for population control without expression of non-native elements or external inducer addition, being potentially exploitable in consortia applications involving precisely defined cell tasks or division of labor.

Stimulation of indigenous microbes by optimizing the water cut in low permeability reservoirs for green and enhanced oil recovery.

Low permeability oil reservoirs are a widespread petroleum reservoir type all over the world. Therefore, methods to recover these reservoirs efficiently are of importance to guarantee energy supply. Here we report our novel stimulation of indigenous microbes by optimizing the water cut in low permeability reservoirs for green and enhanced oil recovery. We aimed to investigate the characteristics of indigenous bacterial communities with changes in water cut in reservoirs by high-throughput sequencing technology, and reveal the mechanism and characteristics of the crude oil biotreatment under different crude oil-water ratio conditions and the optimum activation time of indigenous functional microbial groups in reservoirs. The indigenous microbial metabolism products were characterized by gas chromatography mass spectrometry. Results showed that Acinetobacter (47.1%) and Pseudomones (19.8%) were the main functional genus of crude oil degradation at the optimal activation time, and can reduce the viscosity of crude oil from 8.33 to 5.75 mPa·s. The dominant bacteria genus for oil recovery after activation of the production fluids was similar to those in the reservoirs with water cut of 60-80%. Furthermore seven mechanism pathways of enhancing oil recovery by the synergistic of functional microbial groups and their metabolites under different water cut conditions in low permeability reservoirs have been established.

Use of silicon nanoparticle surface coating in infection control: Experience in a tropical healthcare setting.

BACKGROUND: A nano-scale surface coating containing silicon nanoparticles (Bacterlon®) creates a hydrophobic surface which prevents the growth of bacteria. Study objective was to evaluate the performance of this silicon nano-coating in Sri Lankan healthcare setting. METHODS: This prospective study was conducted from September 2015 to December 2015 in an Intensive Care Unit and a medical ward in Base Hospital Homagama and a bacteriology laboratory in Medical Research Institute, Colombo, Sri Lanka. Silicon nanoparticle coating was applied to 19 high touch surfaces from those three sites. During the follow-up period, these test sites and non-coated control sites were used for routine work and were cleaned routinely as per institute protocol. Swabbing was done for coated and non-coated sites once a week for 12 weeks at unannounced times. Surfaces were categorized in to low (≤10 CFU/cm2) and high (>10-99 CFU/cm2) contamination by Aerobic Bacterial Count (ABC) in non-coated sites at any given time. RESULTS: In low and high contaminated surfaces, an improvement in the mean percentage bioburden reduction from 36.18% to 50.16% was observed from 4th week to 12th week with silicon nanoparticles and a significant reduction (p < 0.05) was seen in ABC in each of the coated surface compared with their non-coated counterpart by the 12th week. The frequency of isolation of Acinetobacter spp. on coated surfaces had a significant reduction (p < 0.01). CONCLUSION: Silicon nanoparticle coating demonstrates a significant reduction of the bacterial bioburden in low and high contaminated surfaces for 12 weeks in a tropical healthcare setting.

Simultaneous removal of Cd2+, NO3-N and hardness by the bacterium Acinetobacter sp. CN86 in aerobic conditions.

This study investigated the factors influencing the simultaneous removal of Cd2+, NO3-N and hardness from water by the bacterial strain CN86. Optimum conditions were determined experimentally by varying the type of organic matter used, initial Cd2+ concentration, and pH. Under the optimum conditions, the maximum removal ratios of Cd2+, NO3-N and hardness were 100.00, 89.85 and 71.63%, respectively. The mechanism of Cd2+ removal is a combination of co-precipitation with calcium carbonate and pH. Further confirmation that Cd2+ can be removed by strain CN86 was provided by XRD and XPS analyses. Meteorological chromatography analysis showed that N2 was produced as an end product. These results demonstrate that the bacterial strain CN86 is a suitable candidate for simultaneously removing Cd2+, NO3-N, and hardness during in wastewater treatment.

Degradation of Perfluorooctane Sulfonamide by Acinetobacter Sp. M and Its Extracellular Enzymes.

The Acinetobacter sp. strain M isolated from a contaminated soil sample in Jiangsu Province of China was found to be able to degrade perfluorooctane sulfonamide (PFOSA) effectively. Fluoride anion (F- ) released from PFOSA degradation was detected by ion chromatography, and showed positive correlation to the growth curve of Acinetobacter sp. strain M. The PFOSA degradation efficiency of strain M was approximately 27 %, as assessed by GC analysis. It was shown that enzymes localized outside of cells of Acinetobacter sp. strain M catalyzed the degradation of PFOSA. This further indicates a possibly new (multi-step/pathway) mechanism for PFOSA degradation. It revealed that the extracellular enzyme of the Acinetobacter strain M preferentially cleaves carbon-carbon and carbon-fluorine bonds instead of destroying the carbon-sulfur bond. The growth condition for Acinetobacter sp. strain M was optimized at 30 °C and pH 7.0 in the presence of 2000 mg L-1 of PFOSA and 0.5 % (v/v) of Tween-20. The optimal PFOSA degradation time was found to be 12 h, with a degradation efficiency of 76 % by extracellular enzymes in strain M as determined by GC analysis. The result may provide potential applications for biodegradition of perfluoro organic compounds, such as derivatives of perfluorooctane (C8).

Acinetobacter baylyi ADP1 growth performance and lipid accumulation on different carbon sources.

Acinetobacter baylyi ADP1 is a microorganism with the potential to produce storage lipids. Here, a systematic study was carried out to evaluate growth performance and accumulation of wax esters and triacylglycerols using glycerol, xylose, glucose, acetate, ethanol, and pyruvate as carbon sources. High specific growth rates (µ) were found in gluconeogenic carbon sources (ethanol, acetate, and pyruvate: 0.94 ± 0.18, 0.93 ± 0.06, and 0.61 ± 0.01 h-1, respectively), and low in glucose (0.25 ± 0.01 h-1). Interestingly, these µ values were sustained in a broad range of concentrations of glucose (0.5-50 g L-1), pyruvate (3-10 g L-1), and acetate (0.3-2 g L-1), suggesting a high tolerance to glucose and pyruvate. It was observed that ADP1 is not able to use glycerol or xylose as unique carbon sources. On the other hand, ADP1 showed sensitivity to osmotic upshifts, noted by the lysis at the beginning of cultivations on different carbon sources. However, ADP1 is adapted to relatively high substrate concentrations as indicated by the minimal inhibitory concentrations (MICs) determined at 24 h of cultivations: 350, 50, 80, and 15 g L-1 for glucose, ethanol, pyruvate, and acetate, respectively. Remarkably, ADP1 co-utilized glucose, acetate, ethanol, and pyruvate. Finally, the accumulation of storage lipids, wax esters (WEs), and triacylglycerols (TAGs) showed to be substrate dependent. Under nitrogen-limiting conditions, the TAGs:WEs (mol:mol) accumulation ratios were 1:4.9 in pyruvate and 1:1.6 in glucose, the WEs were mainly accumulated in acetate. In ethanol, no accumulation of lipids was detected.

Bacterial communities in prepared foods available at supermarkets in Beijing, China.

Prepared foods have received increasing attention owing to their convenience, rapidness, and ease of processing in a fast-paced life. The bacterial diversity and composition vary among different prepared foods and are closely related to food safety and human health. However, the knowledge on the bacterial community in prepared foods is still limited. In this study, the bacterial diversity in three kinds of prepared foods (meat, aquatic, and dish) available at supermarkets in Beijing was examined by using the high throughput sequencing technology to identify bacterial 16S rRNA genes. Alpha diversity analysis indicated that Proteobacteria and Firmicutes were the predominant bacterial phyla in prepared meat products, which accounted for 35-49% and 42-58% of the total sequences, respectively. Similar results were observed in prepared aquatic products, except salmon, which had a relatively unique bacterial community with Proteobacteria accounting for 90.72%. In prepared dishes, the proportions of Proteobacteria and Firmicutes were about 39-74% and 8-37%, respectively. The predominant bacterial genera detected in all samples within each kind of prepared foods were used to examine the differences in the bacterial community among three kinds of prepared foods. Results showed that the bacterial community in prepared meat products was much more diverse (14 genera) than those in prepared aquatic products (6 genera) and prepared dishes (2 genera). Acinetobacter was detected in all 288 prepared products. The bacterial community structures of prepared meat and aquatic products were more similar compared to those of prepared dishes. On the other hand, in prepared meat products, the bacterial communities of the samples with the same materials or brands were more similar, and further, among the sample with the same brands, the bacterial communities of the samples from the development zone were clearly different from those of the samples from the main urban area. In prepared aquatic products, the bacterial communities of the samples from the same region were also more similar. In prepared dish products, the bacterial communities of the samples with the same foodstuff or cooking style were more similar. In conclusion, this study revealed that the origin and type of prepared food ingredients, along with the sales location and processing methods, influenced microbial diversity and composition.