Search

We compared different methods used in single-cell isolation and whole genome amplification of microbial cells, and summarized research progresses in single-cell genomics (SCG) in studying environmental microbes. The studies of single cell and SCG have become one of the hot topics in life sciences in recent years. As a newly developed technology following microbial metagenomics, microbial SCG can efficiently explore large amounts of information of the uncultivable microbial genomics from environment. Generally, following steps need to be taken to obtain microbial SCG:isolation of single microbial cells, whole genome amplification of the single cells, amplicon sequencing, and data analysis. Microbial SCG can be widely used to explore new functional genes that are not detectable by metagenomics and other traditional methods, detect uncultured microbes with extremely low abundance, and study the life evolution of microbial cells.

The regulatory mechanism of bacterial cell division has long been a research focus. Forming a septum at the middle of the cell, the seemingly simple process is involved by multiple regulation factors. Zring (FtsZ ring) is the skeleton of the splitting complex. The locus where Z ring is formed is not only the position the septum formed but also determines the cell division site. Formation of Zring in the incorrect location results in inequality cell division. Several cell division regulation systems have been identified, including the Min system, nucleoid occlusion and the MipZ protein which effectively prevent Zring assembly by different mechanisms, ensuring formation of the fission complex at the correct position. Recent progresses about the formation process of Zring and regulation mechanism affecting the Z-ring positioning are summarized.

Autophagy in intracellular bacterial infection is important. Host cells can use autophagy to eliminate invading pathogens. Meanwhile, autophagy can be exploited, modified or interfered by some pathogens to benefit their survival or proliferation. We reviewed the effect of autophagy on intracellular bacterial infection and discussed our study on the relationship between autophagy and Salmonella infection, which can help provide the theoretical basis for controlling pathogenic infection through regulating and exploiting autophagic pathway.

Similar to multicellular animals, single-cell organisms, such as bacteria show the phenomenon of programmed cell death (PCD). The PCD not only can play an important role in various physiological procedures, but also can eliminate bacteria with irreversible injuries. The PCD of single cell in a colony is for the benefits of other bacteria in the same colony to achieve the development and reproduction of the whole colony. Disturbing or destroying such PCD may provide a new way for antibiotic drug research and development.

Nisin, a lantibiotic produced by some species of Lactococcus lactis, has broad antibacterial spectrum against Gram-positive bacteria species, especially those with close phylogenetic relationship to the nisin producing strain. The broad use of nisin did not lead to widespread resistance. However, some non-nisin producing bacteria could develop certain mechanisms of resistance against nisin when growing under laboratory or nature selection pressure. Nisin resistance mainly involved two strategies, namely, the non-specific physiological isolation mechanism (by the change of cell wall or membrane structure and composition) and the specific protease-mediated mechanism. This review introduced the advances in the study of nisin resistance mechanism.

Objective: To detect, culture, and characterize the nanobacteria (NB) from sera of patients with kidney calculi in our department., Methods: Blood samples of 24 patients with kidney calculi and of 3 healthy volunteers in our department were collected for NB culture in this study. We used immunohistochemistry, von kossa staining, scanning electron microscopy (SEM), transmission electron microscopy (TEM) to investigate the appearance and components of cultural NB., Results: Twenty-two blood samples out of 24 (91.67%) showed growth of NB, while no NB were detected in volunteers' blood samples. The infection rate of stone group was obviously higher than that of healthy volunteers. After a 4-week culture period, the light microscope revealed coccoid-shaped NB with a diameter of 100-500 nm, which could be identified by immunohistochemistry and von kossa staining. SEM and TEM (negative staining) revealed NB with a hollow interior coated in needle-like apatite crystals. Such nanoparticles could bud-off new ones and therefore appeared like living organisms., Conclusion: NB can be identified from sera of most patients involved in kidney calculi. It may have intimate relation to the formation of kidney calculi because the infection rate of NB blood samples of stone patients was significantly higher than that of healthy volunteers. Immunohistochemistry, von kossa staining, SEM and TEM are special methods for identifying NB from different aspects. The appearance and character are important points to distinguish NB from other nano-sized particles.

The effect of immobilized microorganism technique on the micro-polluted river water was studied by four kinds of gaia-biological aerated filter (G-BAF), which were formed by special microorganism (BP35) and four different carriers, including haydite, FPUFS, aquamats flexible carrier and artificial aquatic mat. The removal rates of NH4(+) -N, chlorophyll and turbidity were 83.0%-89.0%, 77.5%-89.0% and 84.4%-95.2%, respectively, and they were all higher than the removal rates of COD, UV254 and TP. The FPUFS contained reactive groups, such as hydroxyl, epoxy and acylamide groups, which made FPUFS load a great amount of enzymes and microorganisms. Therefore, the removal rates of pollutants for FPUFS-G-BAF were higher than those for the other three kinds of G-BAF. Hydraulic retention time (HRT) had little effect on the removal rate of NH4(+) -N, while affected the removal rate of COD significantly. When the concentration of dissolved oxygen (DO) increased from < 2 mg/L to > 4 mg/L, for the four kinds of G-BAF, the removal rates of COD and NH4(+) -N increased 11.9%-18.0% and 12.7%-16.1%, respectively. The result of GC-MS showed that the technique of G-BAF could effectively degrade the macro-molecule refractory organics into small-molecule substance.

Objective: To study the photodynamic inactivation of Gram-positive bacteria Staphylococcus aureus and Gram-negative bacteria Escherichia coli by hematoporyrin monomethyl ether., Methods: Bacteria incubated with different concentrations of hematoporyrin monomethyl ether (HMME) and then irradiated with visual light for 30minutes, bacteria inactivation efficiency was detected with the reduction of colony unit, and morphological changes were observed with atomic force microscope (AFM)., Results: Results indicated that 90% of Staphylococcus aureus was photoinactivated by illumination with visible light for 30 min (power density 200 mW/cm2) in the presence of 50 microg/mL HMME. The bacteria killing efficiency to Staphylococcus aureus with light irradiation was much obvious than that in dark at the same concentration of HMME, although without noticeable damage to E. coli with illumination or in dark. AFM ultrastructure images showed that the cells surface of photodynamic inactivated bacteria was all damaged seriously without the leakage of cell contents., Conclusion: We concluded that the attacked sites to bacteria cells by hematoporyrin monomethyl ether were bacteria membrane structure. Atomic force microscopy provides us a visual technique to study the mechanism of bacteria reacted with photosensitizers.

With four different strains as the model, effects of different culture medium on cell-surface hydrophobicity (CSH) were investigated, and the relationship between CSH, contact time and adhesion of bacteria to activated sludge flocs was correlated. Results showed that culture medium, culture time and the characteristic of strain itself influenced the CSH of bacteria, and initial CSH, contact time was closely related to bacterial adhesion ratio in activated sludge system. When contact time was relatively short (< 14 h), initial CSH was the main factor influencing bacterial adhesion ratio. A critical value existed for CSH, similar bacterial adhesion ratio was obtained below the critical value; beyond the value, bacterial adhesion ratio was greatly enhanced, which indicated that only strains with initial CSH beyond the critical value could adhere to activated sludge flocs rapidly. When contact time was long enough (> or = 38 h), contact time became the main factor influencing adhesion. When the inoculated bacteria thoroughly adhered to sludge flocs by pre-contact, nutrient supplementation and changing oxygen providing mode did not cause the release of adhered bacteria again.

Objective: Examining bacterial diversity in an oil reservoir of Shengli oil field by both culture-independent molecular technique and enrichment method., Methods: The heterotrophic bacteria, hydrocarbon-degrading bacteria and sulfate-reducing bacteria were enriched from S12-4 oil-well samples by the corresponding media. Then the genomic DNAs of the enrichments were extracted and the 16S rRNA gene clone libraries were constructed., Results: The phylogenetic analysis revealed that the bacterial 16S rRNA gene clone libraries of the 3 enrichments were dominated by clones of Thermotoga, Thermaerobacter and Thermotoga, respectively. Sequences of the other co-dominant clones observed only in the enrichments of hydrocarbon-degrading bacteria and sulfate-reducing bacteria were, respectively, associated with Marinobacter and Moorella. The uncultured 16S rRNA gene library was also generated directly from total DNA of S12-4 oil-well samples by bacterial primer set. Sequence analysis of this bacterial library indicated that a large percentage of clones were highly related to the genus Pseudomonas and the dominant species emerging in the enrichment samples had a very low content in the tested oil reservoir. The significant difference of the bacterial composition between the samples obtained from independent-culture method and enrichment method implies that the specialized nutrient may lead to a distinctive selection of dominant organisms., Conclusion: Through culture-dependent and culture-independent methods, we acquired important information on the bacterial diversity of ShengLi oil reservoir. These results may expand our understanding of the microbial diversity of oil reservoir and provide useful information for MEOR(microbial enhancement of oil recovery).

Bioaugmentation with immobilized genetically engineered microorganism (GEM)/conventional activated sludge (CAS) process for treatment of atrazine wastewater was investigated and effects of hydraulic retention time (HRT) on treatment efficiency, activities of GEM were discussed. The results showed that when HRT was 4-24 h, significant removal of atrazine was obtained in the process with bioaugmentation. When the HRT was 24 h, the first stage of the process got best treatment effect: average atrazine removal rate was 96.64% and average atrazine concentration in effluent was 0.56 mg/L. When HRT was changed to 12 h, 8 h or 4 h, the removal rate was 88.59%, 89.79% and 88.61% respectively. The average removal of COD in 4 runs was 72.76%, 64.59%, 66.16% and 65.84% respectively, Significant loss of GEMs was not observed but strong growth activities, formation of biofilm and zoogloea on the surface of immobile particles were observed via scanning electron microscope (SEM). The mechanical stability of the particles remained unchanged after nearly two-month operation.

The packing-type microbial fuel cells (MFCs) were constructed using the granular graphite and the carbon felt as packing materials. The start-up time of the packing-type MFC was about 1 d, which was lower than that of the flat-type MFC. The maximal power density (Pm) of the MFC with carbon felt as packing material was 1502 mW/m2 (37.6 W/m3), which was higher than that with granular graphite as packing material. The carbon felt and carbon paper were sintered together to enhance the electric conductivity. Compared with the flat-type MFC, the area-specific resistance of the packing-type MFC decreased from 0.071 omega x m2 to 0.051 omega x m2, the maximal current density increased from 3000 mA to 8000 mA, the Pm increased from 1100 mW/m2 (27.5 W/m3) to 2426 mW/m2 (60.7 W/m3) and the potentials of anode decreased about 100 mV. The flow rate affected the power generation of the MFC. When the flow rate was lower than 1 mL/min, the Pm dropped with the flux decreasing. The packing-type MFC was operated for over 30 and the coulomb efficiency was about 10.6%.

To detect the metabolic characteristic of rice straw degradation by composite microbial system WSC-6, we cultured WSC-6 in the media used rice straw as the limiting carbon source. The rice straw was added in the style of different quantity once or the same quantity at the different time intervals during 90 days culture. The systems were cultivated under static condition at 50 degrees C. The degradation ratio, absolute degradation quantity,products from degradation and dynamics of pH value of fermentation system were all investigated. The results showed: when 1% rice straw was added once, the pH of fermentation system decreased from initial 7.8 to 6.0 within the first three days inoculation, and after six-day cultivation, it increased to 8.0 and was stable. For dissolved oxygen concentration (DO), the value was maintained at range of 0.01 to 0.12 mg x L(-1) of microaerobic condition. During the rice straw degradation, more than ten kinds of products including ethanol, acetic acid, lactic acid and glycerol and so on were detected using GC-MS. Especially, the highest concentration of lactic acid among all products was 7.381 g x L(-1) at 24 h after inoculation. During 90-day cultivation, for the addition treatments of the different quantity once, the more rice straw added, the quicker and lower the pH decreased, and the longer time intervals returned the pHs were. Especially for 5.0% addition, when 5.0% of rice straw was added once, pH did not increase again after it decreased. Among the addition of the same quantity at the different time intervals, the trend of decrease-increase in pH at 12-day and 15-day intervals could be repeated and high degradation activity well maintained. After 90-day of inoculation, the highest degradation ratio occurred in the treatment at 15-day interval, which was 86.7%. The highest absolute quantity occurred in the treatment at 6-day interval, which was 32.4 g. The trend of pH changes can indicate the activity of lignocellulose degradation and degradation process of the WSC-6.

Based on the satisfactory treatment effect of synthesized oil field wastewater with salinity of 0 - 3%, the salinity effect on the immobilized microorganism in the biological aerated filter (BAF) was further investigated. It was shown that the quantity of live microorganisms could rise to 1.3 x 10(7) per cm3 as the influent salinity was less than 1%, whereas it would decline to 1.1 x 10(6) per cm3 as the salinity increased to 2%, accompanied with the small and cracked cells running out in effluent in the domesticated system. Dehydrogenase activity (DHA) was the highest of 14.4 microg/(mg h) at salinity of 0.5%, which means the greatest degradation capability. And the extra cellular polysaccharide (ECP,) excreted by microorganisms to immobilize themselves on the carriers was the most of 209.9 microg/mg at the salinity of 2%. Although extra cellular polymers (ECP(s)) and microorganisms weight accumulated during the react system operation, the macro-pore diameter of patented FPUFS was from 0.3 to 0.7 mm, which could avoid the clog caused by the microorganisms and their ECP(s), and retained agreeable air and water condition for microorganisms under high salinity.

Contrast to planktonic cells, biofilms are complex communities of microorganisms that develop on biotic or abiotic surfaces. Most of bacteria can form biofilms under proper conditions. Once biofilm form, the inner bacteria cells often exhibit reduced antibiotic susceptibility than their free-floating counterparts, so conventional methods of killing bacteria, such as antibiotics and disinfections are often ineffective with them. Biofilms may cause huge economic loss in equipment damage, product contamination, energy losses and medical infections. Therefore, bacterial biofilm is evolving as a focal problem and an active area of research. As a relatively new area, the progress of biofilm science depends on the development of a satisfactory set of methods. But the classic methods to study planktonic bacteria cannot fulfill the biofilm research, one for which there are few widely accepted methodological standards. Even though biofilms are complicated physical-chemical-biological systems, experience demonstrates that accessible research methods are feasible. In this paper, the theories, principles, merits and limitations of some methods currently used in bacterial biofilm researches, involving artificial biofilm forming and biofilm measurement, were discussed.

Musca domestica,which belongs to insecta, diptera, cyclorrhapha, muscidae, is the most common muscae and the richest resource. It is very significant and valuable to isolate antibacterial peptides from Musca domestica and to develop these peptides into antibacterial medicine. Due to purify a pure peptide from the natural materials (animal, plant and microorganism tissue) is very difficult and complex, few research is going on. It had been reported that the most antibacterial peptides from Musca domestica were alkaline, no weak-acid antibacterial peptides had been reported so far. Based on a high sensitivity detection method, using dilute acetic acid extraction, alginic acid absorption, NaCl salting-out, Sephadex G-25 gel filtration, CMC23 ion-exchange chromatography, electrophoresis, a group of weak-acid antibacterial peptides had been purified from Musca domestica larvae and partial characterized. The peptides had characters of broad antibacterial spectrum and low minimum bactericidal concentration against Gram-positive bacterium such as Bacillus thuringiensis, Bacillus subtilis, Staphylococcus aureus and Gram-negative bacterium such as Pseudomonas aeruginosa, Escherichia coli. The peptides were very stable to keep the antibacterial activity even kept in 95 degrees C for 120 min and frozen-thawed for 10 times. A weak-acid antibacterial peptide MD7095 had been purified in high degree of purity by electro-elution,and was determined Mr 7095Da with MALDI-TOF-MS and pl 5.59 with IEF-PAGE. Peptide mass fingerprinting (PMF) analysis showed MD7095 was a novel bioactive peptide. Few peptides with antibacterial activity against Bacillus thuringiensis had been reported. Observation by scanning electron microscopy (SEM), it was suggested that the bioactivity mechanism of antibacterial peptides from Musca domestica larvae against Bacillus thuringiensis was to perforate cell membrane and lead to bacterium lysis and die. It is hopeful to develop the antibacterial peptides from Musca domestica to candidate medicine.

(Ultra) high pressure had many influences on microbe. It could regulate the expression of gene and protein, influence DNA's structure and function as well as change cell morphology and cell component. These effects not only make (ultra) high pressure to be applied into food sterilization, conserving and some processing, but also indicate it would play an important role in mutagenic breeding of microbe. Pressure can change the structure and function of microbe, yet it is possible that (ultra) high pressure could induce mutation of microbe. Now the feasibility of (ultra) high pressure's mutation effect was discussed according to the effects of it on microbe, some examples and author's studying.