Factors affecting the horizontal patchiness of coastal Antarctic seawater bacteria

Summary Previous Antarctic studies have pointed out the ecological importance of ornithogenic soils. However, few data exist to determine the impact of the bird's manuring on surrounding seawater microbial populations. In order to evaluate the influence of birds manuring, the relationships between the spatial distributions of seawater bacterial microflora and some related biological (chlorophyll pigments) and physicochemical (seston, NH₄ ⁺ & NO₃ ^–) parameters were studied during the Antarctic summer 1988 in the Terre Adelie land area. The clearly decreasing gradient from the shore towards the open sea previously reported for bacterial microflora (from 10⁴ to 1 CFU ml^–1 for heterotrophic bacteria and from 10⁵ to 5.010³ cells ml^–1 for total bacteria) was also observed for organic and mineral nutrients (from 1.09 mg Cl^–1 to 0.1 mg Cl^–1 for POC and from 196 to 17 mole l^–1 for NH ₄ ⁺ ) but not for chlorophyll pigments. The absence of any observable phytoplankton enrichment in the coastal area suggests a direct interaction between the birds manuring and the bacterial seawater microflora.     

Spatial structure of avifauna along urban-rural gradients

We examined the pattern of species composition of breeding birds along urban-rural gradients in the Osaka Prefecture, western Japan. We recorded the proportion of nine types of land-use and the presence/absence of each of 76 breeding birds in 5 km square quadrats on a map of the Prefecture. The proportion of woodland and farmland which increased from urban to rural areas were two major enviornmental gradients according to Principal Component Analysis of the nine types of land-use. Ordination by Canonical Correspondence Analysis (CCA) showed that the breeding bird distribution differentiated along the two major clines, woodland and farmland. The avifauna changed successively along these environmental gradients. There were no discrete boundaries of the distribution of bird species groups. We tentatively classified five groups of quadrats on the ordination plane of the sample score. The geographic position of these five groups on a map preserved the environmental gradient, but showed that water (seashore and river) was a stronger influence on bird species composition than land-use pattern. Although the diversity of land-use seemed to raise species richness in the third group, the less diverse, woodland-rich group contained as many species as the third group. Four groups of bird species, and one group in which species occurred in more than 90% of the quadrats, were classified in the CCA-ordination plane. The occurrence of these bird groups correlated with land-use; the first group with woodland area, the second with scatter woodland, the third with farmland and the fourth with seashore.     

Agarolytic culturable bacteria associated with three antarctic subtidal macroalgae

Bacterial communities of Antarctic marine macroalgae remain largely underexplored in terms of diversity and biotechnological applications. In this study, three Antarctic subtidal macroalgae (Himantothallus grandifolius, Pantoneura plocamioides and Plocamium cartilagineum), two of them endemic of Antarctica, were investigated as a source for isolation of agar-degrading bacteria. A total of 21 epiphytic isolates showed agarolytic activity at low temperature on agar plates containing agar as the sole carbon source. 16S rRNA identification showed that the agar-degrading bacteria belonged to the genera Cellulophaga, Colwellia, Lacinutrix, Olleya, Paraglaciecola, Pseudoalteromonas and Winogradskyella. The agarase enzyme from a potential new species of the genus Olleya was selected for further purification. The enzyme was purified from the culture supernatant of Olleya sp. HG G5.3 by ammonium sulfate precipitation and ion-exchange chromatography. Molecular weight of the agarase was estimated to be 38 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The purified enzyme exhibited activity at 4 °C, retaining >?50% of its maximum activity at this temperature. This is the first study reporting the phylogeny of agar-degrading bacteria isolated from Antarctic subtidal macroalgae and the results suggest the huge potential of Antarctic algae-associated bacteria as a source of cold-active hydrolytic enzymes of biotechnological interest.     

Spatial dependence of stress distribution for rod-shaped bacteria

The stress distribution in the cylindrical portion of the cell envelope of a rod-shaped bacterial cell was compared with that at its polar ends. Using a symmetry argument it is shown that the critical internal pressure for the initiation of yielding of the envelope material has a non-uniform distribution and is significantly higher for the polar regions.     

厦门近海海水中多环芳烃降解菌的原位富集与降解菌多样性

摘要：【目的】为了分析厦门近海原位海水中多环芳烃降解菌的多样性。【方法】将涂有菲的聚氯乙烯（PVC）板悬挂在厦门国际邮轮码头的海水中,进行菲降解菌的原位富集。利用变性梯度凝胶电泳（Denaturing gradient gel electrophoresis,DGGE）和16S rRNA基因文库两种方法分析了在PVC板表面富集微生物的菌群结构。之后,在实验室模拟原位条件下,对PVC板表面富集的菲降解菌群进行进一步富集、分离和初步鉴定。【结果】PVC板在海水中浸没6 d后,16S rRNA基因文库分析表明,在涂菲的PVC板表面富集的菌群中解环菌属（Cycloclasticus）对应的克隆子占文库总克隆子的50%;在未涂菲的PVC板表面吸附的菌群中红杆菌科（Rhodobacteraceae）为优势菌,其对应的克隆子占文库总克隆子的47%;而解环菌属的克隆子只占文库总克隆子的2%。DGGE的分析结果也证明解环菌是菲原位富集降解菌群中的优势菌。实验室进一步富集后,从该菌群中分离鉴定出14株细菌,其中一株新鞘氨醇杆菌B14(Novosphingobium sp.B14)具有菲降解能力。但是,解环菌未能获得纯培养。【结论】菲原位富集发现,厦门近海水体中解环菌是多环芳烃的主要降解菌。     

Spatial distribution of nitrifying (ammonium-oxidizing) bacteria in soil

An experiment in which the effect of increasing periods of chloroform fumigation on nitrification in soil was determined indicated that the active nitrifying bacteria were located at sites in the soil which were readily accessible to diffusing gas. This suggestion was supported by the distribution of potential nitrifying activity in relation to soil pore size, which indicated that nitrifying bacteria were concentrated in soil pores in the size range 136–214 μm.     

Nematophagous fungi from the maritime antarctic: factors affecting distribution

Soil collected from throughout the maritime Antarctic was analyzed to determine the effects of a range of abiotic and biotic soil parameters on the distribution of nematophagous fungi. Endoparasites were far more abundant than predatory fungi due to the greater efficiency of endoparasites in attracting and infecting nematodes, which resulted in a rapid completion of the infection cycle. This allowed endoparasites to colonise even the most exposed soil habitats where conditions favourable for nematode activity were restricted to only a few hours daily. 76% of all endoparasites isolated formed adhesive conidia. The success of this group of endoparasites was due to the ability of the conidia to attract nematodes.Spontaneous trap forming predators were far more abundant than nonspontaneous trap formers. The former have a clear competitive advantage over the latter, as they are able to attract nematodes to the conidia which subsequently germinate and form traps only when induced by direct chemical stimulation of nematodes. These predators are able to use internal reserves only and so rapidly respond to short periods when the soil is unfrozen and the nematodes are active.Although nematodes were utilized by all the species isolated, many were also capable of using Protozoa and Rotifera as a food source. While endoparasites were capable of infecting Rotifera, they were never observed infecting, or were isolated from soil containing, Protozoa. The distribution of endoparasites and spontaneous trap forming predators was largely independent of abiotic soil parameters. They were however significantly associated with the presence and abundance of suitable prey. These species survive solely on nematodes and therefore do not require prolonged periods of suitable soil conditions in order to produce vegetative mycelium to adsorb nutrients saprophytically from the soil, which is a significant ecological advantage over the other groups of microfungi found in the Antarctic.     

Dynamics of virus abundance in coastal seawater

Abstract: The short term dynamics of virus abundance in coastal sea water was investigated by frequent sampling of open ecosystems and of water incubated in bottles in situ. Sampling intervals were 6–10 min. The viral abundance showed significant temporal fluctuations both in situ and in the bottles and it changed in some cases by a factor of 2–4 within 10–20 min. Laboratory incubations showed that production and release of viruses wre not induced or stimulated by nutrient addition, high light intensities or transient increase in temperatures ca. 10°C. Our interpretation of these results is that they result from synchronous lysis and release of virus particles from bacterial hosts and a rapid disintegration of these particles when released in sea water.     

Seasonal distribution of nitrifying bacteria and rates of nitrification in coastal marine sediments

The distribution of nitrification potential (NP) with depth in sediment and season was investigated in a shallow sandy sediment (0.5 m water) and a deeper muddy sediment (17m water). In both sediments, nitrifying bacteria were present in the anoxic strata (oxygen penetration was 5 mm below the surface). The NP at 6–8 cm depth in the sediment was 50% and 10% of the surface NP at the sandy and muddy sediment, respectively. It is suggested that bioturbation and physical disturbance of the sediment were the most likely reasons for this distribution. The NP increased as sediment temperature decreased. This effect was less marked in the muddy sediment. It is concluded that during the summer, the numbers or specific activity of nitrifying bacteria diminished for the following reasons: There was decreased O₂ penetration into the sediment and increased competition for O₂ by heterotrophs; there was increased competition for NH₄ ⁺ and there was inhibition by H₂S. These effects counteracted the potentially higher growth rates and increased rates of NH₄ ⁺ production at the elevated summer temperatures. The potential nitrification rates in the upper 1 cm, which were measured at 22°C, were converted to calculated rates at the in situ temperature (Q₁₀=2.5) and in situ oxygen penetration. These calculated rates were shown to closely resemble the measured in situ rates of nitrification. The relationship between the in situ rates of nitrification and the nitrification potential is discussed.     

The distribution of fluoride in some antarctic seals

Summary The aim of this investigation was to find out why some antarctic seals tolerate fluoride levels in their food (krill) that would be toxic to man. The fluoride content of different soft and hard tissues, urine and feces from 16 L. carcinophagus, 13 L. weddelli and 2 A. tropicalis (urine only) were determined by the fluoride sensitive electrode or by a photometric method (urine). Results and conclusions are following: All soft tissues have low concentrations of fluoride in the same range as soft tissues from non antarctic and non krill eating marine or terrestrial vertebrates. But within the soft tissues there are significant differences in the fluoride content (blood: 0.001 ppm F/dw — brain: 9.1 ppm F/dw). A special tolerance for fluoride of soft tissues can be excluded. Compared with man or weddell-seals the crabeater-seals store two times more fluoride in their skeleton. Hard structures that stop their mineralisation early in the development like teeth have only a relatively low fluoride content. For the same reason only neglectable amounts of fluoride could be detected in hair. Fluoride excretion by the kidneys is efficient and is — besides the storage of fluoride in the skeleton — the second mechanism to guarantee a good blood homoiostasis for fluoride. Until now it is impossible to decide how much fluoride from the food is resorbed by the digestive tract.     

Mortality of fecal bacteria in seawater

We propose a method for determining the mortality rate for allochthonous bacteria released in aquatic environments without interference due to the loss of culturability in specific culture media. This method consists of following the disappearance of radioactivity from the trichloroacetic acid-insoluble fraction in water samples to which [3H]thymidine-prelabeled allochthonous bacteria have been added. In coastal seawater, we found that the actual rate of disappearance of fecal bacteria was 1 order of magnitude lower than the rate of loss of culturability on specific media. Minor adaptation of the procedure may facilitate assessment of the effect of protozoan grazing and bacteriophage lysis on the overall bacterial mortality rate.     

Survival of enteric bacteria in seawater

Enteric bacteria exposed to the marine environment simultaneously encounter a variety of abiotic and biotic challenges. Among the former, light appears to be critical in affecting seawater survival; previous growth history plays a major part in preadaptation of the cells, and stationary phase cells are generally more resistant than exponentially growing ones. Predation, mostly by protozoa, is probably the most significant biotic factor. Using Escherichia coli as a model, a surprisingly small number of genes was found that, when mutated, significantly affect seawater sensitivity of this bacterium. Most prominent among those is rpoS, which was also dominant among genes induced upon transfer to seawater.     

Characterization of antarctic hydrocarbon-degrading bacteria capable of producing bioemulsifiers.

During screening for biosurfactant-producing, n-alkane-degrading marine bacteria, two heterotrophic bacterial strains were isolated from enriched mixed cultures, obtained from Terra Nova Bay (Ross sea, Antarctica) by using aliphatic and artomatic hydrocarbons as the principal carbon source. These gram-positive, aerobic, cocci-shaped bacteria use a various number of organic compounds, including aliphatic hydrocarbons, volatile fatty acids, and biphenyl. During cultivation on n-alkanes as sole source of carbon and energy, all strains produced both an extracellular and cell-bound surface-active mixture of trehalose lipids which reduced the surface tension of water from 72 mN/m to 32mN/m. This class of glycolipids was found to be produced only by marine rhodococci. The 16S-rRNA gene sequence analysis showed that both strains are members of the G + C rich gram-positive group of the phylum Proteobacteria and was found to be almost identical to that of Rhodococcus fascians DSM 20669. The potential of these strains for in situ bioremediation of contaminated cold marine environment is discussed in the present study.     

Spatial distribution of sponge-associated bacteria in the Mediterranean sponge Tethya aurantium

The local distribution of the bacterial community associated with the marine sponge Tethya aurantium Pallas 1766 was studied. Distinct bacterial communities were found to inhabit the endosome and cortex. Clear differences in the associated bacterial populations were demonstrated by denaturing gradient gel electrophoresis (DGGE) and analysis of 16S rRNA gene clone libraries. Specifically associated phylotypes were identified for both regions: a new phylotype of Flexibacteria was recovered only from the sponge cortex, while Synechococcus species were present mainly in the sponge endosome. Light conduction via radiate spicule bundles conceivably facilitates the unusual association of Cyanobacteria with the sponge endosome. Furthermore, a new monophyletic cluster of sponge-derived 16S rRNA gene sequences related to the Betaproteobacteria was identified using analysis of 16S rRNA gene clone libraries. Members of this cluster were specifically associated with both cortex and endosome of T. aurantium.     

Spatiotemporal distribution of marine magnetotactic bacteria in a seasonally stratified coastal salt pond

The occurrence and distribution of magnetotactic bacteria (MB) were studied as a function of the physical and chemical conditions in meromictic Salt Pond, Falmouth, Mass., throughout summer 2002. Three dominant MB morphotypes were observed to occur within the chemocline. Small microaerophilic magnetite-producing cocci were present at the top of the chemocline, while a greigite-producing packet-forming bacterium occurred at the base of the chemocline. The distributions of these groups displayed sharp changes in abundance over small length scales within the water column as well as strong seasonal fluctuations in population abundance. We identified a novel, greigite-producing rod in the sulfidic hypolimnion that was present in relatively constant abundance over the course of the season. This rod is the first MB that appears to belong to the gamma-Proteobacteria, which may suggest an iron- rather than sulfur-based respiratory metabolism. Its distribution and phylogenetic identity suggest that an alternative model for the ecological and physiological role of magnetotaxis is needed for greigite-producing MB.     

Microbial communities related to biodegradation of dispersed Macondo oil at low seawater temperature with Norwegian coastal seawater

The Deepwater Horizon (DWH) accident in 2010 created a deepwater plume of small oil droplets from a deepwater well in the Mississippi Canyon lease block 252 (‘Macondo oil’). A novel laboratory system was used in the current study to investigate biodegradation of Macondo oil dispersions (10 μm or 30 μm median droplet sizes) at low oil concentrations (2 mg l⁻¹) in coastal Norwegian seawater at a temperature of 4–5°C. Whole metagenome analyses showed that oil biodegradation was associated with the successive increased abundances of Gammaproteobacteria, while Alphaproteobacteria (Pelagibacter) became dominant at the end of the experiment. Colwellia and Oceanospirillales were related to n-alkane biodegradation, while particularly Cycloclasticus and Marinobacter were associated with degradation of aromatic hydrocarbons (HCs). The larger oil droplet dispersions resulted in delayed sequential changes of Oceanospirillales and Cycloclasticus, related with slower degradation of alkanes and aromatic HCs. The bacterial successions associated with oil biodegradation showed both similarities and differences when compared with the results from DWH field samples and laboratory studies performed with deepwater from the Gulf of Mexico.     

Spatial distribution and species composition of prosthecate bacteria in Lake Baikal

From the water column of Lake Baikal, several strains of prosthecate bacteria belonging to the genera Caulobacter and Brevundimonas were isolated. In this article, the methods applied for their isolation and cell number determination are described; the occurrence frequency and spatial distribution of these microorganisms in the lake are demonstrated. Characterization of the species composition of cultivable and uncultivable prosthecate bacteria was carried out using the methods of traditional and molecular microbiology, respectively. A comparative phylogenetic analysis of the DNA sequences of uncultivable bacteria, which showed homology to the members of the alpha subclass of proteobacteria, was carried out. It was demonstrated that the lake water column is inhabited by uncultivable alpha-proteobacteria of uncertain phylogenetic affinity, in addition to representatives of the species Caulobacter vibrioides and C. leidyi, which were detected by traditional microbiological methods.     

Thermolabile ribonucleases from antarctic psychrotrophic bacteria: detection of the enzyme in various bacteria and purification from Pseudomonas fluorescens

Abstract Thirteen terrestrial psychrotrophic bacteria from Antarctica were screened for the presence of a thermolabile ribonuclease (RNAase-HL). The enzyme was detected in three isolates of Pseudomonas fluorescens and one isolate of Pseudomonas syringae . It was purified from one P. fluorescens isolate and the molecular mass of the enzyme as determined by SDS-PAGE was 16 kDa. RNAase-HL exhibited optimum activity around 40°C at pH 7.4. It could hydrolyse Escherichia coli RNA and the synthetic substrates poly(A), poly(C), poly(U) and poly(A-U). Unlike the crude RNAase from mesophilic P. fluorescens and pure bovine pancreatic RNAase A which were active even at 65°C, RNAase-HL was totally and irreversibly inactivated at 65°C.     

Spatial and temporal distribution of non-starter lactic acid bacteria in Cheddar cheese

AIMS: The aim of this work was to investigate the spatial and temporal distribution of species and strains of non-starter lactic acid bacteria (NSLAB) within Cheddar cheese. METHODS AND RESULTS: Randomly amplified polymorphic DNA was used to identify and track the principle species and strain groups of NSLAB present. The same strains dominated each location examined within a cheese at any particular time point. Temporal change in species and strains of NSLAB during ripening was observed. A mixture of Lactobacillus paracasei, Lact. plantarum, Lact. rhamnosus and unidentified strains was found up to 6 weeks of maturation, thereafter only Lact. paracasei strains were isolated. CONCLUSION: Little variation in the spatial distribution of NSLAB strains occurs within Cheddar cheese; however, temporal changes in the species and strains were observed during ripening. SIGNIFICANCE AND IMPACT OF THE STUDY: The complex changes in the composition of the NSLAB community of Cheddar cheese may be the source of the variation in flavour that is seen in commercial practice.     

Mortality of fecal bacteria in seawater.

We propose a method for determining the mortality rate for allochthonous bacteria released in aquatic environments without interference due to the loss of culturability in specific culture media. This method consists of following the disappearance of radioactivity from the trichloroacetic acid-insoluble fraction in water samples to which [3H]thymidine-prelabeled allochthonous bacteria have been added. In coastal seawater, we found that the actual rate of disappearance of fecal bacteria was 1 order of magnitude lower than the rate of loss of culturability on specific media. Minor adaptation of the procedure may facilitate assessment of the effect of protozoan grazing and bacteriophage lysis on the overall bacterial mortality rate.