The distribution of endosymbiotic bacteria in different tissues of queens, males, and workers of the carpenter ant
was investigated by light and electron microscopy and by in situ hybridization. A large number of bacteria could be detected in bacteriocytes within the midguts of workers, young virgin queens, and males. Large amounts of bacteria were also found in the oocytes of workers and queens. In contrast, bacteria were not present in oocyte-associated cells or in the spermathecae of mature queens, although occasionally a small number of bacteria could be detected in the testis follicles of males. Interestingly, the number of bacteriocytes in mature queens was strongly reduced and the bacteriocytes contained only very few or no bacteria at all, although the endosymbionts were present in huge amounts in the ovaries of the same animals. During embryogenesis of the deposited egg, the bacteria were concentrated in a ring of endodermal tissue destined to become the midgut in later developmental stages. However, during larval development, bacteria could also be detected in other tissues although to a lesser extent. Only in the last-instar larvae were bacteria found exclusively in the midgut tissue within typical bacteriocytes. Tetracycline and rifampin efficiently cleansed
workers of their symbionts and the bacteriocytes of these animals still remained empty several months after treatment had ceased. Despite the lack of their endosymbionts, these adult animals were able to survive without any obvious negative effect under normal cultivation conditions.
Fluorescent in situ hybridization with a 16S rRNA probe specific for
was used to (i) confirm the division-level identity of and (ii) study the behavior of the obligate intracellular verrucomicrobium “
Xiphinematobacter” in its nematode hosts. Endosymbionts in the egg move to the pole where the gut primordium arises; hence, they populate the intestinal epithelia of juvenile worms. During the host's molt to adult female, the endosymbionts concentrate around the developing ovaries to occupy the ovarian wall. Some bacteria are enclosed in the ripening oocytes for vertical transmission.
in males stay outside the testes because the tiny spermatozoids are not suitable for transmission of cytoplasmic bacteria.
The participation of organisms related to
in full-scale enhanced biological phosphorus removal (EBPR) was investigated. By using fluorescent in situ hybridization techniques, the communities of
-related organisms in two full-scale wastewater treatment plants were estimated to represent between 13 and 18% of the total bacterial population. However, the fractions of these communities that participated in polyphosphate accumulation depended on the type of treatment process evaluated. In a University of Cape Town EBPR process, the percentage of
-related cells that contained polyphosphate was about 20% of the total bacterial population, but these cells represented as much as 73% of the polyphosphate-accumulating organisms (PAOs). In an aerated-anoxic EBPR process,
-related PAOs were less numerous, accounting for 6% of the total bacterial population and 26% of the total PAO population. In addition, 16S ribosomal DNA sequences 99.9% similar to the sequences of
-related organisms enriched in acetate-fed bench-scale EBPR reactors were recovered from both full-scale plants. These results confirmed the involvement of
-related organisms in EBPR and demonstrated their importance in full-scale processes. In addition, the results revealed a significant correlation between the type of EBPR process and the PAO community.