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Water Biology
Published in Frank R. Spellman, The Science of Water, 2020
Bacteria are categorized into three general groups based on their physical form or shape (though almost every variation has been found; see Table 5.3). The simplest form is the sphere. Spherical shaped bacteria are called cocci. Cocci mean “berries.” They are not necessarily perfectly round but may be somewhat elongated, flattened on one side, or oval. Rod-shaped bacteria are called bacilli. Spiral-shaped bacteria (called Spirilla), which have one or more twists and are never straight, make up the third group (see Figure 5.4). Such formations are usually characteristic of a particular genus or species. Within these three groups are many different arrangements. Some exist as single cells; others as pairs, as packets of four or eight, as chains, and as clumps.
Microbiological Aspects
Published in Héctor A. Videla, Manual of Biocorrosion, 2018
Most prokaryotic cells are characterized by a few simple shapes, despite the fact that cellular shape is generally influenced by the environment where the microorganisms live and grow. Generally, sulfate-reducing bacteria (SRB) bacteria are predominant. Some microorganisms present a threadlike aspect, as is frequently found with bacteria growing in water flow systems (filamentous bacteria), and sometimes they present a spiral shape (spirilloid bacteria) or a curved, rod-shape (like a comma) as in the case of bacteria of the genus Vibrio. This type of bacteria, mainly the SRB, play a very important role in biological corrosion. Spherical bacteria are generically called cocci, and according to the type of groups that they form, they can be classified as diplococci (two bacteria), streptococci (chains formed by several cocci), staphylococci (grapeshaped groups of cocci), or tetrads (groups of four cocci together). A summary of the main shapes of bacteria are depicted in Figure 2.2. The limited number of different shapes of bacteria differs markedly from the upper protista, such as fungi or unicellular algae.
Miscellaneous Bacterial Diseases
Published in John A Plumb, Health Maintenance Of Cultured Fishes, 1994
Actual isolation of the bacterium is preferable, but presumptive diagnosis may be accomplished by detecting the Gram-positive coccus (sometimes ovoid) in histological sections or smears from infected tissues. Streptococcus and Enterococcus are not acid fast, motile, capsulated, or spore formers. The bacteria may be single or paired but rarely form chains in infected fish. The organism can be isolated on Todd-Hewitt media, tryptose agar with blood,64 nutrient agar supplemented with rabbit blood,65 or BHI agar with or without the addition of blood. Inoculated media should be incubated at 20 to 30°C, where yellowish to gray, translucent, rounded, slightly raised colonies that are approximately 0.5 to 1.0 mm in diameter are visible at 24 to 48 h. When the streptococci are grown on media (agar or broth) they have more of a tendency to form chains of up to seven or eight cells.
Synergistic combination of cryoprotectants for high freeze-dried survival rate and viable cell counts of Streptococcus thermophilus
Published in Drying Technology, 2023
Lijun Di, Wenlong Ma, Wenli Kang, Yujun Huang, Zhongkun Wu, Boxing Yin, Renqin Yang, Xuecong Liu, Lina Pan, Jiaqi Wang, Li Wei, Ruixia Gu
As shown in Figure 4, the protective effect of 6% sucrose/8% SM/4% Glu-Na on Streptococcus thermophilus Grx02 and Enterococcus faecium 218 was also good, with the survival rates being 95.68 and 92.11%, respectively. At the same time, the protective effect of 6% sucrose/8% SM/4% Glu-Na on two Lactobacillus strains, Lactobacillus plantarum S7 and Lactobacillus fermentum DL02, was compared. It was not good, with the freeze-dried survival rates being 60.3 and 67.7%, respectively. This indicates that the cryoprotectant combination of 6% sucrose/8% SM/4% Glu-Na might be more suitable for Streptococcus thermophilus and Enterococcus faecium than Lactobacillus. However, it cannot be ignored that the bacteria shape has an intrinsic protective effect during the freeze and sublimation processes because the surface area is different between coccus and rods. The larger the surface area of bacterial somatic cells, the greater the damage to the cell membrane and the lower the lyophilized survival rate,[29,30] and the crystallization and migration of the water have different physical injury grades in each kind of bacteria.
Appraisal of suspended growth process for treatment of mixture of simulated petroleum, textile, domestic, agriculture and pharmaceutical wastewater
Published in Environmental Technology, 2020
Precious N. Egbuikwem, Iffat Naz, Devendra P. Saroj
The seed sludge and biomass in reactors 1 and 2 were taken to observe the dynamics of the sludge morphology. SEM images showed that the seed sludge (Figure 6a) was loosely populated by various bacterial micro-colonies mainly coccus, rod-shaped and filamentous-shaped bacteria. Such morphological structures of inoculum sludge have been used for the treatment of synthetic wastewater [56]. After acclimation (day 63) the biomass in the two reactors became densely and multifariously populated by round and both short and long rod-shaped cells covered with exopolysaccharides (EPSs). It implies that during acclimation the microorganisms became well adapted to the conditions of the mixed wastewater, hence became less vulnerable to toxic shock and multiplied. Nevertheless, the EPSs which developed on the biomass structure may have played a vital role in shading the microbial cells against the toxic impact of the mixed wastewater. Similar bacterial colonies have been reported to be dominant in the activated sludge system treating domestic wastewater [44] and textile wastewater [13,57].
A comparative study on membrane fouling alleviation mechanisms by using nanoscale Fe3O4 and poly dimethyldiallylammonium chloride
Published in Environmental Technology, 2020
Jia-heng Zhou, Sheng-feng Jiang, Hao-cheng Yu, Chang-hua Wu, Tao Zeng, Yun-cheng Zhou, Qian-kun Hong, Hong-yu Wang
SEM + EDX were conducted to further visualize the surface morphology. SEM showed sludge flocs in R1 (control reactor) and R6 (with optimal Fe3O4 dosage) were mainly composed of bacillus and coccus (shown in Figure 5(a,b). Rod-shaped bacteria was cross-linked in sludge flocs, and evident nanoscale Fe3O4 (light white dots) embeds in microorganisms matrix (shown in Figure 5(b)). SEM + EDX results of R6 (with optimal Fe3O4 dosage) proved that Fe3O4 (purple dots) were tightly wrapped by microorganisms, and had a uniform distribution in flocs (shown in Figure 5(c)).