Figure 1.
Culturable bacterial concentrations when cultured at three different temperatures (4, 26, and 37°C) in different snow samples and also in an outdoor air sample collected in Beijing from January to March, 2010.
Collected snow samples were melted at room temperature immediately before the analysis; snow data represent averages of five snow samples collected for each snow occurrence on a particular date, and error bars represent standard deviation of three replicates; blank agar plates were used as negative controls.
Figure 2.
Bacterial diversity in snow samples.
[A] PCR-DGGE banding profiles of five different snow samples and an outdoor air sample (540 L) collected in January-March, 2010, Beijing; [B] Dendrograms obtained from the DGGE profiles shown in [A]; the analysis of bacterial diversity in snow samples was based on the mixture of five independent snow samples collected from five locations on each individual date for each snow occurrence.
Figure 3.
PCR-DGGE profiles(A, B, C) of the bacterial diversity of five different snow samples and an outdoor sample collected on different dates of the year 2010 in Beijing.
(A) direct PCR-DGGE; (B) liquid culturing followed by PCR-DGGE, (C) liquid-plate culturing followed by PCR-DGGE; 2–6: snow samples collected in Beijing from five different occurrences that happened on March 14, 8, 1, Feb 7 and January 1 of 2010; the analysis of bacterial diversity in snow samples was based on the mixture of five independent snow samples collected from locations on each individual date; DI water was used as negative control for PCR-DGGE analysis.
Figure 4.
Dendrograms obtained from the DGGE profiles of different snow samples processed as described in Fig.
3. Direct PCR-DGGE, liquid culturing followed by PCR-DGGE, and liquid-plate culturing followed by PCR-DGGE; 2–6: snow samples collected in Beijing from five different snow occurrences that happened on March 14, 8, 1, Feb 7 and January 1 of 2010.
Figure 5.
Neighbour-joining phylogenetic tree showing the relationship of representative sequences of OTUs in all snow samples and reference sequences in GenBank.
It was constructed based on analysis of 16 S rRNA gene sequences of bacteria clone libraries from snow samples. Clone names from 1 (2010) to 4 (2010) represent samples collected on January 1, March 1, 8, 14, Feb 7 of 2010. Clone name 5 (2011) represents snow samples collected on Feb 27 of 2011. The capital “C” in the clone name means Clone. An Escherichia coli strain ATCC 25922 (dq 360844.1) was used as the outgroup.
Table 1.
Dominant fungal species (highest number of colonies obtained per unit of volume) in snow and outdoor air samples collected in Beijing from January to March, 2010.
Figure 6.
Conductance levels of the five different melted snow samples collected in January-March, 2010 in Beijing measured at different modulation frequencies of 1 kHz to 100 kHz by a lock-in amplifier operated at a modulation amplitude of 50 mV.
A LabView program was develoepd to automatically modify the output modulation frequency; data points represent averages of 500 measurements (1 measurement per 300 millisecond); the arrow indicates the conductance transition at the frequency of 10 kHz.
Figure 7.
Average conductance levles measured for five different snow samples collected on different dates and DI water (Millipore) using a lock-in amplifier at a modulation frequency of 100 kHz.
Inset figure represents the conductance averages of the mixture of snow samples collected from five different locations on each individual dates.
Figure 8.
The total organic carbon (TOC) concentrations (mg/L) in snow samples and an outdoor air sample collected in January-March, 2010 in Beijing.
Data points represent averages of the mixture of snow samples collected from five different locations; outdoor air samples were collected using a MCE filter.